Pharmacy Guide

Patient leaflets and SmPCs, drug interaction checker, official dosages and NHS pharmacy opening hours — all in one place.

Pharmacy Guide

Patient leaflets and SmPCs, drug interaction checker, official dosages and NHS pharmacy opening hours — all in one place.

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Paxlovid 150 mg/100 mg film-coated tablets

⚠ This medicine appears to have been discontinued

The electronic medicines compendium (emc) no longer publishes a Summary of Product Characteristics for this product, which usually means it is no longer marketed in the UK. The patient leaflet below is kept for reference, but the product may not be available.

If you were prescribed this medicine, other products containing Nirmatrelvir, Ritonavir may still be available. Do not stop your treatment — ask your pharmacist or GP what to use instead.

Active substance: Nirmatrelvir, Ritonavir
Source: electronic medicines compendium (emc)
Official leaflet: Read the PIL on emc

What it is and what it is used for

for

Paxlovid is an antiviral medicine used for treating mild-to-moderate COVID-19. COVID-19 is caused by a virus. This medicine stops the virus multiplying in cells and this stops the virus multiplying in the body. This can help your body to overcome the virus infection, and may help you get better faster. This medicine contains the active substances nirmatrelvir and ritonavir in two different tablets. Nirmatrelvir is active against the virus that causes COVID-19. Ritonavir prolongs the therapeutic effect of nirmatrelvir. Paxlovid is used in adults 18 years of age and older who do not require supplemental oxygen and who are at increased risk for progression to severe COVID-19, including hospitalisation or death. You must talk to a doctor if you do not feel better or if you feel worse while on treatment with Paxlovid. 2.

What you need to know before you take it

e Paxlovid

Do not take Paxlovid if you are allergic to nirmatrelvir, ritonavir or any of the other ingredients of this medicine (listed in section 6). if you have severe liver disease. if you are taking any of the following medicines. Taking Paxlovid with these medicines may cause serious or life-threatening side effects or affect how Paxlovid works:

• • • • • • • • • • • • • • • • • • • • • • • •

amiodarone, bepridil, dronedarone, encainide, flecainide, propafenone, quinidine (used to treat heart conditions and correct irregular heartbeats) fusidic acid (used to treat bacterial infections) colchicine (used to treat gout) astemizole, terfenadine (used to treat allergies) lurasidone, pimozide (used to treat schizophrenia) quetiapine (used to treat schizophrenia, bipolar disorder, severe depression and abnormal thoughts or feelings) silodosin (used to treat benign prostate enlargement) eplerenone, ivabradine (used to treat heart failure, a condition where the heart is unable to pump enough blood to other parts of the body) dihydroergotamine, ergotamine, eletriptan, ubrogepant (used to treat migraine headaches) ergonovine, methylergonovine (used to stop excessive bleeding that may occur following childbirth or an abortion) cisapride (used to relieve certain stomach problems) voclosporin (used to reduce a specific immune response) lovastatin, simvastatin, lomitapide (used to lower blood cholesterol) finerenone (used to treat chronic kidney disease) naloxegol (used to treat constipation in patients receiving opioid pain killers) avanafil, vardenafil (used to treat erectile dysfunction [also known as impotence]) sildenafil (Revatio®) used to treat pulmonary arterial hypertension (high blood pressure in the pulmonary artery) triazolam, midazolam taken orally (used to relieve anxiety and/or trouble sleeping) flibanserin (used to treat low sexual desire in women who have not gone through menopause) tolvaptan (used to treat cysts in kidneys) carbamazepine, phenobarbital, phenytoin, primidone (used to prevent and control seizures) rifampicin, rifapentine (used to treat tuberculosis) lumacaftor/ivacaftor (used to treat cystic fibrosis) St. John's Wort (Hypericum perforatum) (a herbal remedy used for depression and anxiety)

Warnings and precautions Allergic reactions Allergic reactions, including severe allergic reactions (known as 'anaphylaxis') and serious skin reactions (known as 'toxic epidermal necrolysis' and 'Stevens Johnson syndrome'), can happen in people taking this medicine, even after only 1 dose. Stop taking this medicine and call your doctor right away if you get any of the following symptoms of an allergic reaction: trouble swallowing or breathing swelling of the tongue, mouth, and face throat tightness hoarseness red and painful skin blisters and peeling skin blisters or sores in your mouth or lips Risk of HIV-1 resistance development If you have untreated or uncontrolled HIV infection, Paxlovid may lead to some HIV medicines not working as well in the future. Liver disease Tell your healthcare provider if you have or have had a liver disease. Do not take this medicine if you have severe liver disease. Page 2 of 7

Kidney disease Tell your doctor if you have or have had a kidney disease. Children and adolescents Do not give this medicine to children and adolescents under 18 years because this medicine has not been studied in children and adolescents. Other medicines and Paxlovid There are other medicines that may not be taken together with Paxlovid. Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines, including prescription and over-the-counter medicines, vitamins and herbal supplements. Please tell your doctor if you are taking oral contraceptive pills as you may need to take extra contraceptive precautions such as using a condom (see below 'Pregnancy, breast-feeding and fertility'). In particular, you should inform your doctor or pharmacist if you are taking any of the following:

  • medicines used to treat symptoms of an enlarged prostate, such as tamsulosin
  • medicines used to treat attention disorders, such as amphetamine derivates e.g. methylphenidate and dexamfetamine
  • medicines used to treat severe pain, such as morphine, fentanyl, hydrocodone, oxycodone, meperidine, methadone, buprenorphine, norbuprenorphine and other morphine-like medicines
  • medicines used to treat and correct irregular heartbeats, such as digoxin and disopyramide
  • medicines used to treat asthma and other lung-related problems such as chronic obstructive pulmonary disease (COPD), such as salmeterol and theophylline
  • medicines used to treat cancer, such as afatinib, abemaciclib, apalutamide, ceritinib, dasatinib, nilotinib, vincristine, vinblastine, encorafenib, fostamatinib, ibrutinib and ivosidenib
  • medicines used to thin the blood (anticoagulants), such as warfarin, apixaban, dabigatran, rivaroxaban and vorapaxar
  • medicines used to treat convulsions, such as divalproex and lamotrigine
  • medicines used to treat depressions, such as amitriptyline, fluoxetine, imipramine, nortriptyline, paroxetine, sertraline and desipramine
  • medicines used to treat fungal infections (antifungals), such as itraconazole, ketoconazole and voriconazole
  • medicines used to treat allergies, such as fexofenadine and loratadine
  • medicines used to treat HIV infection, such as atazanavir, darunavir, efavirenz, maraviroc and zidovudine
  • medicines used to treat bacterial infections (antibiotics and antimycobacterials), such as atovaquone, clarithromycin, delamanid, erythromycin, sulfamethoxazole/trimethoprim, bedaquiline and rifabutin
  • medicines used to treat infections by parasites (antiparasitics), such as albendazole
  • medicines used to treat mental or mood disorders, such as clozapine, haloperidol, risperidone, thioridazine, suvorexant, aripiprazole, brexpiprazole, cariprazine, iloperidone, lumateperone and pimavanserin
  • medicines used to treat high blood pressure (hypertension), such as amlodipine, diltiazem, nifedipine, verapamil and aliskiren
  • medicines used to treat heart and/or blood vessel problems, such as ticagrelor, vorapaxar, clopidogrel, cilostazol and mavacamten
  • corticosteroids used to treat inflammation, such as betamethasone, budesonide, ciclesonide, dexamethasone, fluticasone, methylprednisolone, mometasone, prednisolone and triamcinolone
  • medicines used to treat cystic fibrosis, such as ivacaftor, elexacaftor/tezacaftor/ivacaftor, tezacaftor/ivacaftor
  • medicines used to treat diabetes, such as saxagliptin
  • medicines used to treat hepatitis C virus infection, such as glecaprevir/pibrentasvir Page 3 of 7

• • • • • • • • •

medicines used to lower blood cholesterol, such as atorvastatin, fluvastatin, pravastatin and rosuvastatin medicines used to suppress your immune system, such as cyclosporine, tacrolimus, everolimus and sirolimus medicines used to treat inflammatory arthritis, such as tofacitinib and upadacitinib medicines used to treat migraine headaches, such as rimegepant medicines to treat overactive bladder, such as darifenacin medicines used to treat erectile dysfunction (also known as impotence), such as sildenafil and tadalafil medicines used to treat high blood pressure in the blood vessels that supply the lungs, such as tadalafil (Adcirca®), bosentan, and riociguat medicines used as sedatives, hypnotics and sleeping agent, such as alprazolam, buspirone, clonazepam, clorazepate, diazepam, estazolam, flurazepam and zolpidem any of the following other specific medicines: o bupropion (used for smoking cessation) o oral or patch contraceptive containing ethinylestradiol used to prevent pregnancy: barrier or non-hormonal methods of contraception should be considered during the 5 days of Paxlovid treatment and until one menstrual cycle after stopping Paxlovid o midazolam administered by injection (used for sedation [an awake but very relaxed state of calm or drowsiness during a medical test or procedure] or anaesthesia) o levothyroxine (used to treat an underactive thyroid gland [hypothyroidism])

Many medicines interact with Paxlovid. Keep a list of your medicines to show your doctor and pharmacist. Do not start taking a new medicine without telling your doctor. Your doctor can tell you if it is safe to take Paxlovid with other medicines. Pregnancy, breast-feeding and fertility There is not enough information to be sure that Paxlovid is safe for use in pregnancy and it is not known if this medicine will harm your baby while you are pregnant. If you are pregnant, it is not recommended to use this medicine unless your clinical condition requires this treatment. If you are pregnant, think you may be pregnant, or are planning to have a baby, ask your doctor for advice before taking this medicine. If you can become pregnant, it is recommended that you refrain from sexual activity or use effective barrier contraception while taking this medicine and until after one full menstrual cycle is completed after stopping the treatment. If you are breast-feeding or are planning to breastfeed, tell your healthcare provider before taking this medicine. A small amount of Paxlovid passes into breast milk. You should not breast-feed your baby while taking this medicine and for 48 hours after completing the treatment as a precaution. Driving and using machines Paxlovid has not been specifically tested for its possible effects on the ability to drive a car or operate machines. Paxlovid contains lactose (a type of sugar) If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicinal product. Information on sodium content This medicine contains less than 1 mmol sodium (23 mg) per dose, that is to say essentially 'sodium-free'. 3.

How to take it

Paxlovid

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Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure. Paxlovid consists of 2 medicines: nirmatrelvir and ritonavir. A course of treatment lasts 5 days. Swallow the tablets whole. Do not chew, break or crush the tablets. This medicine can be taken with or without meals. Recommended dose The recommended dose is 2 tablets of nirmatrelvir with 1 tablet of ritonavir by mouth twice daily (in the morning and in the evening). The blister foil for each day of treatment is divided in two different coloured sections to indicate which tablets need to be taken at each time of day – one side for the morning (AM) dose and the other side for the evening (PM) dose. If you have MILD kidney disease, follow the above recommended dosage. If you have MODERATE kidney disease, the recommended dose is 1 tablet of nirmatrelvir with 1 tablet of ritonavir by mouth twice daily (in the morning and in the evening). The blister foil for each day of treatment is divided in two different coloured sections – one side for the morning (AM) dose and the other side for the evening (PM) dose – but each of these sections contain one extra tablet of nirmatrelvir that is not needed. If you have SEVERE kidney disease, the recommended dose is 2 tablets of nirmatrelvir with 1 tablet of ritonavir by mouth once on Day 1, and then 1 tablet of nirmatrelvir with 1 tablet of ritonavir once daily on Days 2 to 5. The daily dose pack contains more tablets than needed and the coloured sections of the blister foil (AM and PM) for each day of treatment can be ignored since the tablets need to be taken only once daily. Use in children and adolescents Paxlovid is not used to treat children and adolescents (under 18 years old). If you take more Paxlovid than you should If you take too much of this medicine, call your healthcare provider or go to the nearest hospital emergency room right away. If you forget to take Paxlovid If you forget to take a dose of this medicine, take it as soon as you remember. If more than 8 hours have passed since your missed dose, then do not take the missed dose and just carry on as before. Do not take a double dose to make up for a forgotten dose. If you feel better Even if you feel better, do not stop taking this medicine without talking to your healthcare provider. If you have any further questions on the use of this medicine, ask your doctor or pharmacist. 4.

Possible side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them. Not many people have taken Paxlovid. Serious and unexpected side effects may happen. Common: may affect up to 1 in 10 people

  • Diarrhoea
  • Nausea
  • Altered sense of taste (such as metallic, bitter taste)
  • Headache Page 5 of 7

Uncommon: may affect up to 1 in 100 people

  • Allergic reaction (such as hives, trouble swallowing or breathing, swelling of the mouth, lips, or face, throat tightness, hoarseness or skin rash)
  • Vomiting
  • Abdominal pain
  • High blood pressure Rare: may affect up to 1 in 1,000 people
  • Severe allergic reaction known as 'anaphylaxis' (such as swelling of tongue, mouth and face, trouble swallowing or breathing, throat tightness, or hoarseness)
  • Serious skin reactions known as 'toxic epidermal necrolysis' and 'Stevens-Johnson syndrome' (such as red and painful skin, blisters and peeling skin, blisters or sores in your mouth or lips)
  • Feeling generally unwell Reporting of side effects If you get any side effects, talk to your doctor or pharmacist. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Coronavirus Yellow Card Reporting site at https://coronavirus-yellowcard.mhra.gov.uk or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine. 5.

How to store it

Paxlovid

Keep this medicine out of the sight and reach of children. Do not use this medicine after the expiry date which is stated on the carton or the blister after 'EXP'. The expiry date refers to the last day of that month. This medicinal product does not require any special storage conditions. Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment. 6.

Contents of the pack and other information

What Paxlovid contains The active substances in this medicine are nirmatrelvir and ritonavir. Each pink film-coated nirmatrelvir tablet contains 150 mg of nirmatrelvir. Each white film-coated ritonavir tablet contains 100 mg of ritonavir. The other ingredients in nirmatrelvir are microcrystalline cellulose, lactose monohydrate (see section 2, 'Paxlovid contains lactose'), croscarmellose sodium, colloidal silicon dioxide and sodium stearyl fumarate. The film-coating contains hypromellose (E464), titanium dioxide (E171), macrogol (E1521) and iron oxide red (E172). The other ingredients in ritonavir are copovidone, sorbitan laurate, silica colloidal anhydrous (E551), calcium hydrogen phosphate and sodium stearyl fumarate. The film-coating contains hypromellose (E464), titanium dioxide (E171), macrogol (E1521), hydroxypropyl cellulose (E463), talc (E553b), silica colloidal anhydrous (E551) and polysorbate 80 (E433). What Paxlovid looks like and contents of the pack Nirmatrelvir 150 mg film-coated tablets are pink, oval-shaped and debossed with 'PFE' on one side and '3CL' on the other side.

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Ritonavir 100 mg film-coated tablets are white to off white, capsule-shaped and debossed with 'H' on one side and 'R9' on the other side. Twice daily dose blister card Paxlovid tablets are available in 5 daily-dose blister cards with a total of 30 tablets packaged in a carton. Each daily blister card contains 4 nirmatrelvir tablets (150 mg each) and 2 ritonavir tablets (100 mg each) and indicates which tablets need to be taken in the morning and evening. Once daily dose blister card Paxlovid tablets are available in a 5-day blister card with a total of 11 tablets packaged in a carton. The 5-day blister card contains 6 nirmatrelvir tablets (150 mg each) and 5 ritonavir tablets (100 mg each) and indicates which tablets need to be taken once daily for 5 days. Not all pack sizes may be marketed. Marketing Authorisation Holder Pfizer Limited Ramsgate Road Sandwich, Kent CT13 9NJ United Kingdom Manufacturers Pfizer Manufacturing Deutschland GmbH Mooswaldallee 1 79108 Freiburg Im Breisgau Germany Pfizer Italia S.r.l. Localita Marino del Tronto 631000 Ascoli, Piceno Italy Pfizer Ireland Pharmaceuticals Unlimited Company Little Connell Newbridge Co. Kildare W12 HX57 Ireland For any information about this medicine, please contact: Medical Information, Pfizer Ltd, Walton Oaks, Dorking Road, Tadworth, Surrey, KT20 7NS. Telephone 01304 616161. This leaflet was last revised in 05/2026. This medicine has been given 'conditional approval'. This means that there is more evidence to come about this medicine. The Agency will review new information on this medicine at least every year and this leaflet will be updated as necessary. Ref: PX 25_0

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Frequently asked questions about Paxlovid 150 mg/100 mg film-coated tablets

How do I take Paxlovid 150 mg/100 mg film-coated tablets?

Paxlovid 150 mg/100 mg film-coated tablets comes as tablet containing 150mg / 100mg. Always follow the dose your doctor or pharmacist has given you, and read the leaflet that comes with the medicine.

What is the active substance in Paxlovid 150 mg/100 mg film-coated tablets?

The active substance in Paxlovid 150 mg/100 mg film-coated tablets is nirmatrelvir, ritonavir.

Where does this information come from?

This leaflet reproduces the patient information leaflet approved for Paxlovid 150 mg/100 mg film-coated tablets, as published on the electronic medicines compendium (emc). The version printed inside your medicine’s packaging is the one that applies to you.

Can I get Paxlovid 150 mg/100 mg film-coated tablets without a prescription?

Whether a medicine is available over the counter or on prescription only depends on its licence. Check the leaflet, or ask your pharmacist — they can tell you straight away.

About this leaflet

The text above reproduces the patient information leaflet approved for this medicine, restructured for easier reading.

Medical disclaimer: This page is for information only and does not replace advice from your doctor or pharmacist. Always read the leaflet supplied with your medicine. If you are unwell, call NHS 111; in an emergency, call 999.

Medicines with the same active substance: Nirmatrelvir, ritonavir (1 medicine), Ritonavir (6 medicines)
See every medicine containing this substance, or browse the full A–Z of active substances.
⚕For healthcare professionals — Summary of Product Characteristics (SmPC)Full SmPC: dosage, interactions, contraindications, warnings+
Technical information intended for healthcare professionals (doctors and pharmacists). The Summary of Product Characteristics (SmPC) is the official document approved by the MHRA/EMA. It does not replace the patient leaflet or a doctor’s advice.

4.1. Therapeutic indications

Paxlovid is indicated for the treatment of COVID‑19 in adults who do not require supplemental oxygen and who are at increased risk for progression to severe COVID‑19 (see section 5.1).

4.2. Posology and method of administration

Paxlovid is nirmatrelvir tablets co-packaged with ritonavir tablets.

Nirmatrelvir must be coadministered with ritonavir. Failure to correctly coadminister nirmatrelvir with ritonavir will result in plasma concentrations of nirmatrelvir that will be insufficient to achieve the desired therapeutic effect.

Posology

The recommended dosage is 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) all taken together orally twice daily every 12 hours for 5 days. Paxlovid should be given as soon as possible after positive results of direct SARS-CoV-2 viral testing and within 5 days of onset of symptoms even if baseline COVID-19 symptoms are mild.

A missed dose should be taken as soon as possible and within 8 hours of the scheduled time, and the normal dosing schedule should be resumed. If more than 8 hours has elapsed, the missed dose should not be taken and the treatment should resume according to the normal dosing schedule.

If a patient requires hospitalisation due to severe or critical COVID-19 after starting treatment with Paxlovid, the patient should complete the full 5-day treatment course at the discretion of his/her healthcare provider.

Special populations

Paediatric population

The safety and efficacy of Paxlovid in paediatric patients younger than 18 years of age have not yet been established.

Elderly

No dosage adjustment is currently recommended for elderly patients.

Renal impairment

No dosage adjustment is needed in patients with mild renal impairment [estimated glomerular filtration rate (eGFR) ≥ 60 to < 90 mL/min].

In patients with moderate renal impairment (eGFR ≥ 30 to < 60 mL/min) or with severe renal impairment (eGFR < 30 mL/min) including those requiring haemodialysis, the dosage of Paxlovid should be reduced as shown in Table 1. Paxlovid should be administered at approximately the same time each day for 5 days. On days patients with severe renal impairment undergo haemodialysis, the Paxlovid dose should be administered after haemodialysis (see section 5.2).

Table 1: Recommended dose and regimen for patients with renal impairment

Renal function

Days of treatment

Dose and dose frequencya

Moderate renal impairment

(eGFR ≥ 30 to < 60 mL/min)

Days 1-5

150 mg nirmatrelvir (one 150 mg tablet) with 100 mg ritonavir (one 100 mg tablet) twice daily

Severe renal impairment

(eGFR < 30 mL/min) including those requiring haemodialysisb

Day 1

300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) once

Days 2-5

150 mg nirmatrelvir (one 150 mg tablet) with 100 mg ritonavir (one 100 mg tablet) once daily

Abbreviation: eGFR=estimated glomerular filtration rate.

a. Paxlovid should be administered at approximately the same time each day for 5 days.

b. On days of hemodialysis, the Paxlovid dose should be administered after hemodialysis.

Special attention for patients with severe renal impairment

Healthcare providers should pay special attention to dosing instructions for patients with severe renal impairment and alert the patient that the daily dose pack provided may contain more nirmatrelvir and ritonavir tablets than needed for accurate dosing in these patients.

Therefore, patients with severe renal impairment should be alerted that two tablets of nirmatrelvir with one tablet of ritonavir should be taken once on day 1 followed by one tablet of nirmatrelvir with one tablet of ritonavir once daily on days 2 to 5.

Special attention for patients with moderate renal impairment

Healthcare providers should pay special attention to dosing instructions for patients with moderate renal impairment and alert the patient that the daily dose pack provided may contain more nirmatrelvir and ritonavir tablets than needed for accurate dosing in these patients.

Therefore, patients with moderate renal impairment should be alerted that only one tablet of nirmatrelvir with one tablet of ritonavir should be taken every 12 hours for 5 days.

The remaining tablets should be disposed of in accordance with local requirements (see section 6.6).

Hepatic impairment

No dosage adjustment of Paxlovid is needed for patients with either mild (Child-Pugh Class A) or moderate (Child-Pugh Class B) hepatic impairment.

No pharmacokinetic or safety data are available regarding the use of nirmatrelvir or ritonavir in subjects with severe (Child-Pugh Class C) hepatic impairment, therefore, Paxlovid is contraindicated in patients with severe hepatic impairment (see sections 4.3 and 5.2).

Concomitant therapy with ritonavir- or cobicistat-containing regimen

No dosage adjustment is needed; the dose of Paxlovid is 300 mg/100 mg twice daily for 5 days.

Patients diagnosed with human immunodeficiency virus (HIV) or hepatitis C virus (HCV) infection who are receiving ritonavir- or cobicistat-containing regimen should continue their treatment as indicated.

Method of administration

For oral use.

Paxlovid can be taken with or without food (see section 5.2). The tablets should be swallowed whole and not chewed, broken or crushed.

4.3. Contraindications

Paxlovid is contraindicated in patients:

- with a history of clinically significant hypersensitivity to the active substances (nirmatrelvir/ritonavir) or to any of the excipients listed in section 6.1.

- with severe hepatic impairment.

Paxlovid is also contraindicated with medicinal products that are highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life‑threatening reactions. Paxlovid is also contraindicated with medicinal products that are potent CYP3A inducers where significantly reduced plasma nirmatrelvir/ritonavir concentrations may be associated with the potential for loss of virologic response and possible resistance. Medicinal products listed in Table 2 and Table 3 (section 4.5) are a guide and not considered a comprehensive list of all possible medicinal products that may be contraindicated with Paxlovid.

Table 2: Medicinal products that are contraindicated for concomitant use with nirmatrelvir/ritonavir

Medicinal product class

Medicinal products within class

Clinical comments

Interactions that result in increased concentrations of concomitant medicinal product as Paxlovid inhibits their CYP3A4 metabolic pathway

Alpha1‑adrenoreceptor antagonist

alfuzosin

Increased plasma concentrations of alfuzosin may lead to severe hypotension.

Antianginal

ranolazine

Potentially increased plasma concentrations of ranolazine may result in serious and/or life-threatening reactions.

Anticancer agents

neratinib

venetoclax

Increased plasma concentrations of neratinib which may increase the potential for serious and/or life‑threatening reactions including hepatotoxicity.

Increased plasma concentrations of venetoclax which may increase the risk of tumour lysis syndrome at the dose initiation and during the dose-titration phase.

Antiarrhythmics

amiodarone,

bepridil,

dronedarone,

encainide,

flecainide,

propafenone,

quinidine

Potentially increased plasma concentrations of amiodarone, bepridil, dronedarone, encainide, flecainide, propafenone and quinidine may result in arrhythmias or other serious adverse effects.

Antibiotic

fusidic acid

Increased plasma concentrations of fusidic acid and ritonavir.

Anti-gout

colchicine

Increased plasma concentrations of colchicine may result in serious and/or life-threatening reactions in patients with renal and/or hepatic impairment.

Antihistamines

astemizole,

terfenadine

Increased plasma concentrations of astemizole and terfenadine may result in serious arrhythmias from these agents.

Antipsychotics/neuroleptics

lurasidone,

pimozide

quetiapine

Increased plasma concentrations of lurasidone and pimozide result in serious and/or life‑threatening reactions.

Increased plasma concentrations of quetiapine may lead to coma.

Benign prostatic hyperplasia agents

silodosin

Increased plasma concentrations of benign prostatic hyperplasia agent.

Cardiovascular agents

eplerenone,

ivabradine

Increased plasma concentrations of cardiovascular agents.

Ergot derivatives

dihydroergotamine,

ergonovine,

ergotamine,

methylergonovine

Increased plasma concentrations of ergot derivatives leading to acute ergot toxicity, including vasospasm and ischaemia.

GI motility agent

cisapride

Increased plasma concentrations of cisapride, thereby increasing the risk of serious arrhythmias from this agent.

Immunosuppressants

voclosporin

Increased plasma concentrations of immunosuppressant.

Lipid-modifying agents

HMG-CoA reductase inhibitors

Microsomal triglyceride transfer protein (MTTP) inhibitor

lovastatin,

simvastatin

lomitapide

Increased plasma concentrations of lovastatin and simvastatin resulting in increased risk of myopathy, including rhabdomyolysis.

Increased plasma concentrations of lomitapide.

Migraine medications

eletriptan,

ubrogepant

Increased plasma concentrations of migraine medications.

Mineralocorticoid receptor antagonists

finerenone

Increased plasma concentrations of mineralocorticoid receptor antagonist.

Opioid antagonists

naloxegol

Increased plasma concentrations of opioid antagonist.

PDE5 inhibitors

avanafil,

vardenafil

sildenafil (Revatio®) when used for pulmonary arterial hypertension (PAH)

Increased plasma concentrations of avanafil and vardenafil.

Increased plasma concentrations of sildenafil can potentially result in visual abnormalities, hypotension, prolonged erection and syncope.

Sedative/hypnotics

triazolam,

oral midazolama

Increased plasma concentrations of triazolam and oral midazolam can increase risk of extreme sedation and respiratory depression.

Serotonin receptor 1A agonists/serotonin receptor 2A antagonists

flibanserin

Increased plasma concentrations of serotonin receptor 1A agonist/serotonin receptor 2A antagonist.

Vasopressin receptor antagonists

tolvaptan

Increased plasma concentrations of vasopressin receptor antagonist.

Interactions that result in decreased concentrations of nirmatrelvir/ritonavir as the concomitant medicinal products induce Paxlovid's CYP3A4 metabolic pathway

Anticonvulsants

carbamazepinea,

phenobarbital,

phenytoin,

primidone

Decreased plasma concentrations of nirmatrelvir/ritonavir may lead to loss of virologic response and possible resistance.

Anticancer agents

enzalutamide

Decreased plasma concentrations of nirmatrelvir/ritonavir may lead to loss of virologic response and possible resistance.

Antimycobacterials

rifampicin, rifapentine

Potentially decreased plasma concentrations of nirmatrelvir/ritonavir may lead to loss of virologic response and possible resistance.

Cystic fibrosis transmembrane conductance regulator potentiators

lumacaftor/ivacaftor

Potentially decreased plasma concentrations of nirmatrelvir/ritonavir may lead to loss of virologic response and possible resistance.

Herbal products

St. John's Wort (Hypericum perforatum)

Potentially decreased plasma concentrations of nirmatrelvir/ritonavir may lead to loss of virologic response and possible resistance.

a. See section 5.2, Interaction studies conducted with nirmatrelvir/ritonavir.

4.4. Special warnings and precautions for use

Risk of serious adverse reactions due to interactions with other medicinal products

Initiation of Paxlovid, a CYP3A inhibitor, in patients receiving medicinal products metabolised by CYP3A or initiation of medicinal products metabolised by CYP3A in patients already receiving Paxlovid, may increase plasma concentrations of medicinal products metabolised by CYP3A.

Initiation of medicinal products that inhibit or induce CYP3A may increase or decrease concentrations of Paxlovid, respectively.

These interactions may lead to:

• Clinically significant adverse reactions, potentially leading to severe, life-threatening or fatal events from greater exposures of concomitant medicinal products.

• Clinically significant adverse reactions from greater exposures of Paxlovid.

• Loss of therapeutic effect of Paxlovid and possible development of viral resistance.

Severe, life-threatening, and fatal adverse reactions due to drug interactions have been reported in patients treated with Paxlovid.

See Table 1 for medicinal products that are contraindicated for concomitant use with nirmatrelvir/ritonavir (see section 4.3) and Table 2 for potentially significant interactions with other medicinal products (see section 4.5). Potential for interactions should be considered with other medicinal products prior to and during Paxlovid therapy; concomitant medicinal products should be reviewed during Paxlovid therapy and the patient should be monitored for the adverse reactions associated with the concomitant medicinal products. The risk of interactions with concomitant medications during the 5-day treatment period for Paxlovid should be weighed against the risk of not receiving Paxlovid.

Coadministration of Paxlovid with calcineurin inhibitors and mTOR inhibitors

Consultation of a multidisciplinary group (e.g., involving physicians, specialists in immunosuppressive therapy, and/or specialists in clinical pharmacology) is required to handle the complexity of this coadministration by closely and regularly monitoring immunosuppressant blood concentrations and adjusting the dose of the immunosuppressant in accordance with the latest guidelines (see section 4.5).

Hypersensitivity reactions

Anaphylaxis, hypersensitivity reactions, and serious skin reactions (including toxic epidermal necrolysis and Stevens-Johnson syndrome) have been reported with Paxlovid (see section 4.8). If signs and symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, immediately discontinue Paxlovid and initiate appropriate medications and/or supportive care.

Hepatotoxicity

Hepatic transaminase elevations, clinical hepatitis and jaundice have occurred in patients receiving ritonavir. Therefore, caution should be exercised when administering Paxlovid to patients with pre-existing liver diseases, liver enzyme abnormalities or hepatitis.

HIV resistance

As nirmatrelvir is coadministered with ritonavir, there may be a risk of HIV-1 developing resistance to HIV protease inhibitors in individuals with uncontrolled or undiagnosed HIV-1 infection.

Excipients

Lactose

Nirmatrelvir tablets contain lactose. Patients with rare hereditary problems of galactose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medicine.

Sodium

Nirmatrelvir and ritonavir tablets each contain less than 1 mmol sodium (23 mg) per tablet, that is to say essentially 'sodium‑free'.

4.5. Interaction with other medicinal products and other forms of interaction

Paxlovid (nirmatrelvir/ritonavir) is a strong inhibitor of CYP3A and an inhibitor of CYP2D6, P-gp and OATP1B1. Coadministration of Paxlovid with medicinal products that are primarily metabolised by CYP3A and CYP2D6 or are transported by P-gp or OATP1B1 may result in increased plasma concentrations of such medicinal products and increase the risk of adverse reactions.

Medicinal products that are extensively metabolised by CYP3A and have high first pass metabolism appear to be the most susceptible to large increases in exposure when coadministered with nirmatrelvir/ritonavir. Thus, coadministration of Paxlovid with medicinal products highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life‑threatening events is contraindicated (see Table 1, section 4.3).

In vitro study results showed nirmatrelvir may be inducer of CYP3A4, CYP2B6, CYP2C8, and CYP2C9. The clinical relevance is unknown. Based on in vitro data, nirmatrelvir has a low potential to inhibit BCRP, MATE2K, OAT1, OAT3, OATP1B3 and OCT2. There is a potential for nirmatrelvir to inhibit MDR1, MATE1, OCT1 and OATP1B1 at clinically relevant concentrations.

Ritonavir has a high affinity for several cytochrome P450 (CYP) isoforms and may inhibit oxidation with the following ranked order: CYP3A4 > CYP2D6. Ritonavir also has a high affinity for P‑glycoprotein (P-gp) and may inhibit this transporter. Ritonavir may induce glucuronidation and oxidation by CYP1A2, CYP2C8, CYP2C9 and CYP2C19 thereby increasing the biotransformation of some medicinal products metabolised by these pathways and may result in decreased systemic exposure to such medicinal products, which could decrease or shorten their therapeutic effect.

Coadministration of other CYP3A4 substrates that may lead to potentially significant interaction should be considered only if the benefits outweigh the risks (see Table 2).

Nirmatrelvir/ritonavir is a CYP3A substrate; therefore, medicinal products that induce CYP3A may decrease plasma concentrations of nirmatrelvir and ritonavir and reduce Paxlovid therapeutic effect.

Medicinal products listed in Table 2 (section 4.3) and Table 3 are a guide and not considered a comprehensive list of all possible medicinal products that may interact with nirmatrelvir/ritonavir. The healthcare provider should consult appropriate references for comprehensive information.

Table 3: Interaction with other medicinal products and other forms of interaction

Medicinal product class

Medicinal product within class

(AUC change, Cmax Change)

Clinical comments

Alpha1‑adrenoreceptor antagonist

↑alfuzosin

↑tamsulosin

Increased plasma concentrations of alfuzosin may lead to severe hypotension and is therefore contraindicated (see section 4.3).

Avoid concomitant use with Paxlovid.

Amphetamine derivatives

↑methylphenidate, ↑dexamfetamine

Ritonavir dosed as an antiretroviral agent is likely to inhibit CYP2D6 and as a result is expected to increase concentrations of amphetamine and its derivatives. Careful monitoring of adverse effects is recommended when these medicines are coadministered with Paxlovid.

Analgesics

↑buprenorphine (57%, 77%),

↑norbuprenorphine (33%, 108%)

↑fentanyl

↑hydrocodone

↑oxycodone

↑meperidine

↓methadone (36%, 38%)

↓morphine

The increases of plasma levels of buprenorphine and its active metabolite did not lead to clinically significant pharmacodynamic changes in a population of opioid tolerant patients. Adjustment to the dose of buprenorphine may therefore not be necessary when the two are dosed together.

Ritonavir dosed as a pharmacokinetic enhancer inhibits CYP3A4 and as a result is expected to increase the plasma concentrations of these medicines. Careful monitoring of therapeutic and adverse effects (including respiratory depression) is recommended when fentanyl, hydrocodone, oxycodone, or meperidine is concomitantly administered with Paxlovid. If concomitant use with Paxlovid is necessary, consider a dosage reduction of the narcotic analgesic and monitor patients closely at frequent intervals. Refer to the individual SmPC for more information.

Increased methadone dose may be necessary when coadministered with ritonavir dosed as a pharmacokinetic enhancer due to induction of glucuronidation. Dose adjustment should be considered based on the patient's clinical response to methadone therapy.

Morphine levels may be decreased due to induction of glucuronidation by coadministered ritonavir dosed as a pharmacokinetic enhancer.

Antianginal

↑ranolazine

Due to CYP3A inhibition by ritonavir, concentrations of ranolazine are expected to increase. The concomitant administration with ranolazine is contraindicated (see section 4.3).

Antiarrhythmics

↑amiodarone, ↑dronedarone, ↑flecainide, ↑propafenone, ↑quinidine

↑digoxin

↑disopyramide

Ritonavir coadministration is likely to result in increased plasma concentrations of amiodarone, dronedarone, flecainide, propafenone and quinidine and is therefore contraindicated (see section 4.3).

This interaction may be due to modification of P-gp mediated digoxin efflux by ritonavir dosed as a pharmacokinetic enhancer.

Caution is warranted and therapeutic concentration monitoring is recommended for antiarrhythmic if available.

Antiasthmatic

↓theophylline (43%, 32%)

An increased dose of theophylline may be required when coadministered with ritonavir, due to induction of CYP1A2.

Anticancer agents

enzalutamide

↑afatinib

↑abemaciclib

↑apalutamide

↑ceritinib

↑dasatinib, ↑nilotinib, ↑vincristine, ↑vinblastine

↑encorafenib

↑fostamatinib

↑ibrutinib

↑neratinib

↑venetoclax

Coadministration contraindicated due to potential loss of virologic response and possible resistance (see section 4.3).

Serum concentrations may be increased due to Breast Cancer Resistance Protein (BCRP) and acute P-gp inhibition by ritonavir. The extent of increase in AUC and Cmax depends on the timing of ritonavir administration. Caution should be exercised in administering afatinib with Paxlovid (refer to the afatinib SmPC). Monitor for ADRs related to afatinib.

Serum concentrations may be increased due to CYP3A4 inhibition by ritonavir.

Coadministration of abemaciclib and Paxlovid should be avoided. If this coadministration is judged unavoidable, refer to the abemaciclib SmPC for dose adjustment recommendations. Monitor for ADRs related to abemaciclib.

Apalutamide is a moderate to strong CYP3A4 inducer and this may lead to a decreased exposure of nirmatrelvir/ritonavir and potential loss of virologic response. In addition, serum concentrations of apalutamide may be increased when coadministered with ritonavir resulting in the potential for serious adverse events including seizure. Concomitant use of Paxlovid with apalutamide is not recommended.

Serum concentrations of ceritinib may be increased due to CYP3A and P-gp inhibition by ritonavir. Caution should be exercised in administering ceritinib with Paxlovid. Refer to the ceritinib SmPC for dose adjustment recommendations. Monitor for ADRs related to ceritinib.

Serum concentrations may be increased when coadministered with ritonavir resulting in the potential for increased incidence of adverse events.

Serum concentrations of encorafenib may be increased when coadministered with ritonavir which may increase the risk of toxicity, including the risk of serious adverse events such as QT interval prolongation. Coadministration of encorafenib and ritonavir should be avoided. If the benefit is considered to outweigh the risk and ritonavir must be used, patients should be carefully monitored for safety.

Coadministration of fostamatinib with ritonavir may increase fostamatinib metabolite R406 exposure resulting in dose-related adverse events such as hepatotoxicity, neutropenia, hypertension or diarrhoea. Refer to the fostamatinib SmPC for dose reduction recommendations if such events occur.

Serum concentrations of ibrutinib may be increased due to CYP3A inhibition by ritonavir, resulting in increased risk for toxicity including risk of tumour lysis syndrome. Coadministration of ibrutinib and ritonavir should be avoided. If the benefit is considered to outweigh the risk and ritonavir must be used, reduce the ibrutinib dose to 140 mg and monitor patient closely for toxicity.

Serum concentrations may be increased due to CYP3A4 inhibition by ritonavir.

Concomitant use of neratinib with Paxlovid is contraindicated due to serious and/or life-threatening potential reactions including hepatotoxicity (see section 4.3).

Serum concentrations may be increased due to CYP3A inhibition by ritonavir, resulting in increased risk of tumour lysis syndrome at the dose initiation and during the ramp-up phase (see section 4.3 and refer to the venetoclax SmPC). For patients who have completed the ramp-up phase and are on a steady daily dose of venetoclax, reduce the venetoclax dose by at least 75% when used with strong CYP3A inhibitors (refer to the venetoclax SmPC for dosing instructions).

Anticoagulants

↑apixaban

↑dabigatrana (194%, 233%)

↑rivaroxaban (153%, 53%)

↑vorapaxar

warfarin,

↑↓S-warfarin (9%, 9%),

↓↔R-warfarin (33%)

Combined P-gp and strong CYP3A4 inhibitors increase blood levels of apixaban and increase the risk of bleeding. Dosing recommendations for coadministration of apixaban with Paxlovid depend on the apixaban dose. Refer to the apixaban SmPC for more information.

Increased bleeding risk with dabigatran. Depending on dabigatran indication and renal function, reduce dose of dabigatran or avoid concomitant use. Refer to the dabigatran SmPC for further information.

Inhibition of CYP3A and P-gp lead to increased plasma levels and pharmacodynamic effects of rivaroxaban which may lead to an increased bleeding risk. Therefore, the use of ritonavir is not recommended in patients receiving rivaroxaban.

Serum concentrations may be increased due to CYP3A inhibition by ritonavir. The coadministration of vorapaxar with Paxlovid is not recommended (refer to the vorapaxar SmPC).

Induction of CYP1A2 and CYP2C9 lead to decreased levels of R-warfarin while little pharmacokinetic effect is noted on S‑warfarin when coadministered with ritonavir. Decreased R-warfarin levels may lead to reduced anticoagulation, therefore it is recommended that anticoagulation parameters are monitored when warfarin is coadministered with ritonavir.

Anticonvulsants

carbamazepinea

phenobarbital, phenytoin, primidone

↓divalproex, ↓lamotrigine

Carbamazepine is strong CYP3A4 inducer, and this may lead to a decreased exposure of nirmatrelvir and ritonavir and potential loss of virologic response. Concomitant use of carbamazepine with Paxlovid is contraindicated (see section 4.3).

Coadministration contraindicated due to potential loss of virologic response and possible resistance (see section 4.3).

Ritonavir dosed as a pharmacokinetic enhancer induces oxidation by CYP2C9 and glucuronidation and as a result is expected to decrease the plasma concentrations of anticonvulsants. Careful monitoring of serum levels or therapeutic effects is recommended when these medicines are coadministered with ritonavir.

Antidepressants

↑amitriptyline, ↑fluoxetine, ↑imipramine, ↑nortriptyline, ↑paroxetine, ↑sertraline

↑desipramine (145%, 22%)

Ritonavir dosed as an antiretroviral agent is likely to inhibit CYP2D6 and as a result is expected to increase concentrations of imipramine, amitriptyline, nortriptyline, fluoxetine, paroxetine or sertraline.

Careful monitoring of therapeutic and adverse effects is recommended when these medicines are concomitantly administered with antiretroviral doses of ritonavir.

The AUC and Cmax of the 2-hydroxy metabolite were decreased 15% and 67%, respectively. Dosage reduction of desipramine is recommended when coadministered with ritonavir.

Antifungals

↑ketoconazole (3.4-fold, 55%)

↑itraconazolea

↓voriconazole (39%, 24%)

Ritonavir inhibits CYP3A-mediated metabolism of ketoconazole. Due to an increased incidence of gastrointestinal and hepatic adverse reactions, a dose reduction of ketoconazole should be considered when coadministered with ritonavir.

Ritonavir dosed as a pharmacokinetic enhancer inhibits CYP3A4 and as a result is expected to increase the plasma concentrations of itraconazole. Careful monitoring of therapeutic and adverse effects is recommended when itraconazole is coadministered with ritonavir.

Coadministration of voriconazole and ritonavir dosed as a pharmacokinetic enhancer should be avoided, unless an assessment of the benefit/risk to the patient justifies the use of voriconazole.

Anti-gout

↑colchicine

Concentrations of colchicine are expected to increase when coadministered with ritonavir. Life-threatening and fatal drug interactions have been reported in patients treated with colchicine and ritonavir (CYP3A4 and P-gp inhibition).

Concomitant use of colchicine with Paxlovid is contraindicated (see section 4.3).

Antihistamines

↑fexofenadine

↑loratadine

Ritonavir may modify P-gp mediated fexofenadine efflux when dosed as a pharmacokinetic enhancer resulting in increased concentrations of fexofenadine.

Ritonavir dosed as a pharmacokinetic enhancer inhibits CYP3A and as a result is expected to increase the plasma concentrations of loratadine. Careful monitoring of therapeutic and adverse effects is recommended when loratadine is coadministered with ritonavir.

Anti-HIV protease inhibitors

↑atazanavir (86%, 11-fold)

↑darunavir (14-fold)

Ritonavir increases the serum levels of atazanavir as a result of CYP3A4 inhibition. For further information, physicians should refer to the SmPC for atazanavir.

Ritonavir increases the serum levels of darunavir as a result of CYP3A inhibition. Darunavir must be given with ritonavir to ensure its therapeutic effect. For further information, refer to the SmPC for darunavir.

Anti-HIV

↑efavirenz (21%)

↑maraviroc (161%, 28%)

↓zidovudine (25%, ND)

A higher frequency of adverse reactions (e.g., dizziness, nausea, paraesthesia) and laboratory abnormalities (elevated liver enzymes) have been observed when efavirenz is coadministered with ritonavir.

Ritonavir increases the serum levels of maraviroc as a result of CYP3A inhibition. Maraviroc may be given with ritonavir to increase the maraviroc exposure. For further information, refer to the SmPC for maraviroc.

Ritonavir may induce the glucuronidation of zidovudine, resulting in slightly decreased levels of zidovudine. Dose alterations should not be necessary.

Anti-infectives

↓atovaquone

↑clarithromycin (77%, 31%)

↓14-OH clarithromycin metabolite (100%, 99%)

delamanid

↑erythromycin

↑fusidic acid

sulfamethoxazole/trimethoprim

Ritonavir dosed as a pharmacokinetic enhancer induces glucuronidation and as a result is expected to decrease the plasma concentrations of atovaquone. Careful monitoring of serum levels or therapeutic effects is recommended when atovaquone is coadministered with ritonavir.

Due to the large therapeutic window of clarithromycin no dose reduction should be necessary in patients with normal renal function. Clarithromycin doses greater than 1 g per day should not be coadministered with ritonavir dosed as a pharmacokinetic enhancer. For patients with renal impairment, a clarithromycin dose reduction should be considered: for patients with creatinine clearance of 30 to 60 ml/min the dose should be reduced by 50%, for patients with creatinine clearance less than 30 ml/min the dose should be reduced by 75%.

No interaction study is available with ritonavir only. In a healthy volunteer drug interaction study of delamanid 100 mg twice daily and lopinavir/ritonavir 400/100 mg twice daily for 14 days, the exposure of the delamanid metabolite DM‑6705 was 30% increased. Due to the risk of QTc prolongation associated with DM-6705, if coadministration of delamanid with ritonavir is considered necessary, very frequent ECG monitoring throughout the full delamanid treatment period is recommended (see section 4.4 and refer to the delamanid SmPC).

Ritonavir dosed as a pharmacokinetic enhancer inhibits CYP3A4 and as a result is expected to increase the plasma concentrations of erythromycin. Careful monitoring of therapeutic and adverse effects is recommended when erythromycin is coadministered with ritonavir.

Ritonavir coadministration is likely to result in increased plasma concentrations of both fusidic acid and ritonavir and is therefore contraindicated (see section 4.3).

Dose alteration of sulfamethoxazole/trimethoprim during concomitant ritonavir therapy should not be necessary.

Antimycobacterial

↑bedaquiline

↑rifabutin (4-fold, 2.5-fold)

↑25-O-desacetyl rifabutin metabolite (38-fold, 16-fold)

rifampicin, rifapentine

No interaction study is available with ritonavir only. Due to the risk of bedaquiline related adverse events, coadministration should be avoided. If the benefit outweighs the risk, coadministration of bedaquiline with ritonavir must be done with caution. More frequent electrocardiogram monitoring and monitoring of transaminases is recommended (refer to the bedaquiline SmPC).

Due to the large increase in rifabutin AUC, reduction of the rifabutin dose to 150 mg 3 times per week may be indicated when coadministered with ritonavir as a pharmacokinetic enhancer.

Rifampicin and rifapentine are strong CYP3A4 inducers, and this may lead to a decreased exposure of nirmatrelvir/ritonavir and potential loss of virologic response. Concomitant use of rifampicin and rifapentine with Paxlovid is contraindicated (see section 4.3).

Antiparasitic agent

↓albendazole

Significant decreases in plasma concentrations of albendazole and its active metabolite may occur due to induction by ritonavir, with a risk of decreased albendazole efficacy. Clinical monitoring of therapeutic response and possible adjustment of albendazole dosage during treatment with Paxlovid and following discontinuation is recommended.

Antipsychotics

↑lurasidone, ↑pimozide

↑quetiapine

↑clozapine

↑haloperidol, ↑risperidone, ↑thioridazine

Due to CYP3A inhibition by ritonavir, concentrations of lurasidone and pimozide are expected to increase. The concomitant administration with lurasidone and pimozide is contraindicated (see section 4.3).

Due to CYP3A inhibition by ritonavir, concentrations of quetiapine are expected to increase. Concomitant administration of Paxlovid and quetiapine is contraindicated as it may increase quetiapine-related toxicity (see section 4.3).

If coadministration is necessary, consider reducing the clozapine dose and monitor for adverse reactions.

Ritonavir is likely to inhibit CYP2D6 and as a result is expected to increase concentrations of haloperidol, risperidone and thioridazine. Careful monitoring of therapeutic and adverse effects is recommended when these medicines are concomitantly administered with antiretroviral doses of ritonavir.

Benign prostatic hyperplasia agents

↑silodosin

Coadministration contraindicated due to potential for postural hypotension (see section 4.3).

Calcium channel antagonist

↑amlodipine, ↑diltiazem, ↑nifedipine, ↑verapamil

Ritonavir dosed as a pharmacokinetic enhancer or as an antiretroviral agent inhibits CYP3A4 and as a result is expected to increase the plasma concentrations of calcium channel antagonists. Careful monitoring of therapeutic and adverse effects is recommended when these medicines are concomitantly administered with ritonavir.

Cardiovascular agents

↑eplerenone

↑ivabradine

↑aliskiren, ↑ticagrelor, ↑vorapaxar

↓clopidogrel

↑cilostazol

↑mavacamten

Coadministration with eplerenone is contraindicated due to potential for hyperkalaemia (see section 4.3).

Coadministration with ivabradine is contraindicated due to potential for bradycardia or conduction disturbances (see section 4.3).

Avoid concomitant use with Paxlovid.

Coadministration is likely to result in decreased plasma concentrations of the active metabolite of clopidogrel.

Dosage adjustment of cilostazol is recommended. Refer to the cilostazol SmPC for more information.

Coadministration with mavacamten may increase mavacamten plasma concentration and increase the risk of heart failure. Discontinue mavacamten for the duration of Paxlovid treatment. Resumption of mavacamten within 5 days of completing Paxlovid may result in higher exposure of mavacamten. Refer to the mavacamten SmPC for more information.

Corticosteroids primarily metabolized by CYP3A

↑betamethasone, ↑budesonide, ↑ciclesonide, ↑fluticasone, ↑methylprednisolone, ↑mometasone, ↑triamcinolone

↑dexamethasone

Coadministration with corticosteroids (all routes of administration) of which exposures are significantly increased by strong CYP3A inhibitors can increase the risk for Cushing's syndrome and adrenal suppression. However, the risk of Cushing's syndrome and adrenal suppression associated with short-term use of a strong CYP3A4 inhibitor is low.

Alternative corticosteroids including beclomethasone and prednisone should be considered.

Ritonavir dosed as a pharmacokinetic enhancer or as an antiretroviral agent inhibits CYP3A and as a result is expected to increase the plasma concentrations of dexamethasone. Careful monitoring of therapeutic and adverse effects is recommended when dexamethasone is concomitantly administered with ritonavir.

Corticosteroids

↑prednisolone (28%, 9%)

Careful monitoring of therapeutic and adverse effects is recommended when prednisolone is concomitantly administered with ritonavir. The AUC of the metabolite prednisolone increased by 37 and 28% after 4 and 14 days ritonavir, respectively.

Cystic fibrosis transmembrane conductance regulator potentiators

lumacaftor/ivacaftor

↑ivacaftor,

↑elexacaftor/ tezacaftor/ivacaftor, ↑tezacaftor/ivacaftor

Coadministration contraindicated due to potential loss of virologic response and possible resistance (see section 4.3).

Reduce dosage when coadministered with Paxlovid. Refer to the individual product SmPC for more information.

Dipeptidyl peptidase 4 (DPP4) inhibitors

↑saxagliptin

Dosage adjustment of saxagliptin is recommended. Refer to the saxagliptin SmPC for more information.

Endothelin antagonists

↑bosentan

Coadministration of bosentan and ritonavir may increase steady-state bosentan Cmax and AUC.

Ergot derivatives

↑dihydroergotamine, ↑ergonovine, ↑ergotamine, ↑methylergonovine

Ritonavir coadministration is likely to result in increased plasma concentrations of ergot derivatives and is therefore contraindicated (see section 4.3)

HCV direct acting antiviral

↑glecaprevir/pibrentasvir

Serum concentrations may be increased due to P-gp, BCRP and OATP1B inhibition by ritonavir. Concomitant administration of glecaprevir/pibrentasvir and Paxlovid is to be avoided due to an increased risk of ALT elevations associated with increased glecaprevir exposure.

Herbal products

St. John's Wort (Hypericum perforatum)

Coadministration contraindicated due to potential loss of virologic response and possible resistance (see section 4.3).

HMG-CoA reductase inhibitors

↑lovastatin, ↑simvastatin

↑atorvastatin, ↑rosuvastatina

↑fluvastatin, ↑pravastatin,

Since increased concentrations of lovastatin and simvastatin may predispose patients to myopathies, including rhabdomyolysis, the combination of these medicinal products with ritonavir is contraindicated (see section 4.3).

Discontinue use of lovastatin and simvastatin at least 12 hours prior to initiation of Paxlovid, during the 5 days of Paxlovid treatment and for 5 days after completing Paxlovid.

Consider temporary discontinuation of atorvastatin and rosuvastatin during treatment with Paxlovid. Atorvastatin and rosuvastatin do not need to be held prior to or after completing Paxlovid

The metabolism of pravastatin and fluvastatin is not dependent on CYP3A, and interactions are not expected with ritonavir. If treatment with an HMG-CoA reductase inhibitor is indicated, pravastatin or fluvastatin is recommended.

Hormonal contraceptive

↓ethinylestradiol (40%, 32%)

Due to reductions in ethinylestradiol concentrations, barrier or other non‑hormonal methods of contraception should be considered during the 5 days of Paxlovid treatment and until one menstrual cycle after stopping Paxlovid. Ritonavir is likely to change the uterine bleeding profile and reduce the effectiveness of estradiol-containing contraceptives.

Immunosupressants

↑voclosporin

Calcineurin inhibitors: ↑cyclosporine, ↑tacrolimus

mTOR inhibitors: ↑everolimus, ↑sirolimus

Coadministration contraindicated due to potential for acute and/or chronic nephrotoxicity (see section 4.3).

Avoid concomitant use of calcineurin inhibitors and mTOR inhibitors during treatment with Paxlovid.

Dose adjustment of the immunosuppressant and close and regular monitoring for immunosuppressant concentrations and immunosuppressant-associated adverse reactions is are recommended during and after treatment with Paxlovid. Refer to the individual immunosuppressant SmPC and latest guidelines for further information and obtain expert consultation of a multidisciplinary group (see section 4.4).

Janus kinase (JAK) inhibitors

↑tofacitinib

↑upadacitinib

Dosage adjustment of tofacitinib is recommended. Refer to the tofacitinib SmPC for more information.

Dosing recommendations for coadministration of upadacitinib with Paxlovid depends on the upadacitinib indication. Refer to the upadacitinib SmPC for more information.

Long-acting beta‑adrenoceptor agonists

↑salmeterol

Ritonavir inhibits CYP3A4 and as a result a pronounced increase in the plasma concentrations of salmeterol is expected. Therefore, avoid concomitant use with Paxlovid.

Microsomal triglyceride transfer protein (MTTP) inhibitors

↑lomitapide

CYP3A4 inhibitors increase the exposure of lomitapide, with strong inhibitors increasing exposure approximately 27‑fold. Due to CYP3A inhibition by ritonavir, concentrations of lomitapide are expected to increase. Concomitant use of Paxlovid with lomitapide is contraindicated due to potential for hepatotoxicity and gastrointestinal adverse reactions (refer to the lomitapide SmPC) (see section 4.3).

Migraine medications

↑eletriptan

↑ubrogepant

↑rimegepant

Coadministration of eletriptan within at least 72 hours of Paxlovid is contraindicated due to potential for serious adverse reactions including cardiovascular and cerebrovascular events (see section 4.3).

Coadministration of ubrogepant with Paxlovid is contraindicated due to potential for serious adverse reactions (see section 4.3).

Avoid concomitant use with Paxlovid.

Mineralocorticoid receptor antagonists

↑finerenone

Coadministration contraindicated due to potential for serious adverse reactions including hyperkalaemia, hypotension, and hyponatremia (see section 4.3).

Muscarinic receptor antagonists

↑darifenacin

The darifenacin daily dose should not exceed 7.5 mg when coadministered with Paxlovid. Refer to the darifenacin SmPC for more information.

Neuropsychiatric agents

↑suvorexant

↑aripiprazole, ↑brexpiprazole, ↑cariprazine, ↑iloperidone, ↑lumateperone, ↑pimavanserin

Avoid concomitant use of suvorexant with Paxlovid.

Dosage adjustment of aripiprazole, brexpiprazole, cariprazine, iloperidone, lumateperone, and pimavanserin is recommended. Refer to the individual SmPC for more information.

Opioid antagonists

↑naloxegol

Coadministration contraindicated due to the potential for opioid withdrawal symptoms (see section 4.3).

PDE5 inhibitors (Erectile dysfunction agents)

↑avanafil (13-fold, 2.4-fold)

↑sildenafil (11-fold, 4-fold), ↑tadalafil (124%, ↔)

↑vardenafil (49-fold, 13-fold)

Concomitant use of avanafil with Paxlovid is contraindicated (see section 4.3) because a safe and effective avanafil dosage regimen has not been established.

Dosage adjustment is recommended for use of sildenafil or tadalafil with Paxlovid. Concomitant use of sildenafil or tadalafil for the treatment of erectile dysfunction with ritonavir dosed as an antiretroviral agent or as a pharmacokinetic enhancer should be made with caution and and with increased monitoring for adverse reactions. Sildenafil doses should not exceed 25 mg in 48 hours and tadalafil doses should be reduced to no more than 10 mg every 72 hours. Refer to individual product SmPC for more information.

Concomitant use of vardenafil with Paxlovid is contraindicated (see section 4.3).

PDE5 inhibitors (Pulmonary hypertension agents)

↑sildenafil (Revatio®)

↑tadalafil (Adcirca®)

Coadministration of sildenafil with Paxlovid is contraindicated due to the potential for sildenafil associated adverse events, including visual abnormalities, hypotension, prolonged erection, and syncope (see section 4.3).

Avoid concomitant use of tadalafil with Paxlovid.

sGC stimulators (Pulmonary hypertension agents)

↑riociguat

Dosage adjustment is recommended for riociguat. Refer to the riociguat SmPC for more information.

Sedatives/hypnotics

↑oral (1430%, 368%) and parenteral midazolama

↑triazolam (> 20-fold, 87%)

↑alprazolam (2.5-fold, ↔)

↑buspirone, ↑clonazepam, ↑clorazepate, ↑diazepam, ↑estazolam, ↑flurazepam

↑zolpidem (28%, 22%)

Midazolam is extensively metabolised by CYP3A4. Coadministration with Paxlovid may cause a large increase in the concentration of midazolam.

Plasma concentrations of midazolam are expected to be significantly higher when midazolam is given orally. Therefore, Paxlovid should not be coadministered with orally administered midazolam (see section 4.3), whereas caution should be used with coadministration of Paxlovid and parenteral midazolam. Data from concomitant use of parenteral midazolam with other protease inhibitors suggests a possible 3 – 4 fold increase in midazolam plasma levels. If Paxlovid is coadministered with parenteral midazolam, it should be done in an intensive care unit (ICU) or similar setting which ensures close clinical monitoring and appropriate medical management in case of respiratory depression and/or prolonged sedation. Dosage adjustment for midazolam should be considered, especially if more than a single dose of midazolam is administered.

Ritonavir coadministration is likely to result in increased plasma concentrations of triazolam and is therefore contraindicated (see section 4.3)

Alprazolam metabolism is inhibited following the introduction of ritonavir. Caution is warranted during the first several days when alprazolam is coadministered with ritonavir dosed as an antiretroviral agent or as a pharmacokinetic enhancer, before induction of alprazolam metabolism develops.

Ritonavir dosed as a pharmacokinetic enhancer or as an antiretroviral agent inhibits CYP3A and as a result is expected to increase the plasma concentrations of buspirone, clonazepam, clorazepate, diazepam, estazolam, and flurazepam. A dose decrease may be needed for these medicinal products when coadministered with Paxlovid and careful monitoring of therapeutic and adverse effects is recommended when concomitantly administered with Paxlovid.

Zolpidem and ritonavir may be coadministered with careful monitoring for excessive sedative effects.

Serotonin receptor 1A agonists/ serotonin receptor 2A antagonists

↑flibanserin

Coadministration contraindicated due to potential for hypotension, syncope, and CNS depression (see section 4.3).

Smoke cessation

↓bupropion (22%, 21%)

Bupropion is primarily metabolised by CYP2B6. Concurrent administration of bupropion with repeated doses of ritonavir is expected to decrease bupropion levels. These effects are thought to represent induction of bupropion metabolism. However, because ritonavir has also been shown to inhibit CYP2B6 in vitro, the recommended dose of bupropion should not be exceeded. In contrast to long-term administration of ritonavir, there was no significant interaction with bupropion after short‑term administration of low doses of ritonavir (200 mg twice daily for 2 days), suggesting reductions in bupropion concentrations may have onset several days after initiation of ritonavir coadministration.

Thyroid hormone replacement therapy

levothyroxine

Post-marketing cases have been reported indicating a potential interaction between ritonavir containing products and levothyroxine. Thyroid-stimulating hormone (TSH) should be monitored in patients treated with levothyroxine at least the first month after starting and/or ending ritonavir treatment.

Vasopressin receptor antagonists

↑tolvaptan

Coadministration contraindicated due to potential for dehydration, hypovolemia and hyperkalaemia (see section 4.3).

Abbreviations: ALT=alanine aminotransferase, AUC=area under the curve; Cmax=maximum concentrations.

a. See section 5.2 Interaction studies conducted with nirmatrelvir/ritonavir.

4.6. Fertility, pregnancy and lactation

Women of childbearing potential/Contraception in males and females

There are limited human data on the use of Paxlovid during pregnancy to inform the drug-associated risk of adverse developmental outcomes, women of childbearing potential should avoid becoming pregnant during treatment with Paxlovid.

Use of ritonavir may reduce the efficacy of combined hormonal contraceptives. Patients using combined hormonal contraceptives should be advised to use an effective alternative contraceptive method or an additional barrier method of contraception during treatment and until after one complete menstrual cycle after stopping Paxlovid (see section 4.5).

Pregnancy

There are limited data from the use of Paxlovid in pregnant women. Paxlovid should be used during pregnancy only if the potential benefits outweigh the potential risks for the mother and the foetus.

Animal data with nirmatrelvir have shown developmental toxicity in the rabbit (lower foetal body weights) but not in the rat. There was no nirmatrelvir-related effect on foetal morphology or embryo-foetal viability at any dose tested in rat or rabbit embryo-foetal developmental toxicity studies. There were no nirmatrelvir-related adverse effects in a pre- and postnatal developmental study in rats (see section 5.3).

A large number (6100 live births) of pregnant women were exposed to ritonavir during pregnancy; of these, 2800 live births were exposed during the first trimester. These data largely refer to exposures where ritonavir was used in combination therapy and not at therapeutic ritonavir doses but at lower doses as a pharmacokinetic enhancer for other protease inhibitors, similar to the ritonavir dose used for nirmatrelvir/ritonavir. These data indicate no increase in the rate of birth defects compared to rates observed in population-based birth defect surveillance systems. Animal data with ritonavir have shown reproductive toxicity (see section 5.3).

Breast-feeding

In a clinical pharmacokinetics study, 8 healthy lactating women who were at least 12 weeks postpartum were administered 3 doses (steady-state dosing) of 300 mg/100 mg nirmatrelvir/ritonavir. Nirmatrelvir and ritonavir were excreted in breastmilk in small amounts, with a milk to plasma AUC ratio of 0.26 and 0.07, respectively. The mean (range) estimated daily infant dose (assuming average milk consumption of 150 mL/kg/day), was 1.8% (1.3-2.5%) and 0.2% (0.1-0.3%) of the maternal dose.

There are no available data on the effects of nirmatrelvir or ritonavir on the breast‑fed newborn/infant or on milk production. A risk to the newborn/infant cannot be excluded. Breast‑feeding should be discontinued during treatment with Paxlovid and for 48 hours after the last dose of Paxlovid.

Fertility

There are no human data on the effect of Paxlovid on fertility. No human data on the effect of nirmatrelvir on fertility are available. Nirmatrelvir produced no effects on fertility in rats (see section 5.3).

There are no human data on the effect of ritonavir on fertility. Ritonavir produced no effects on fertility in rats.

4.7. Effects on ability to drive and use machines

There are no clinical studies that evaluated the effects of Paxlovid on ability to drive and use machines.

4.8. Undesirable effects

Summary of the safety profile

The safety of Paxlovid was based on data from three phase 2/3 randomised, placebo-controlled trials in non‑hospitalised adult participants with a laboratory confirmed diagnosis of SARS-CoV-2 infection (see section 5.1).

• Study C4671005 (EPIC-HR) and Study C4671002 (EPIC-SR) investigated Paxlovid (nirmatrelvir/ritonavir 300 mg/100 mg) every 12 hours for 5 days in symptomatic participants with a laboratory confirmed diagnosis of SARS-CoV-2 infection. Participants were to present with mild-to-moderate COVID-19 at baseline.

• Study C4671006 (EPIC-PEP) investigated Paxlovid (nirmatrelvir/ritonavir 300 mg/100 mg) every 12 hours for 5 or 10 days in asymptomatic household contact of individuals with a recent diagnosis of SARS-CoV-2 infection. Participants were to have a negative SARS-CoV-2 result at baseline.

Across the three studies, 3,515 participants received a dose of Paxlovid and 2,585 participants received a dose of placebo. The most common adverse reactions (≥1% incidence in the Paxlovid group and occurring at a greater frequency than in the placebo group) were dysgeusia (5.9% and 0.4%, respectively) and diarrhoea (2.9% and 1.9%, respectively).

The safety profile of Paxlovid in participants with severe renal impairment, including those requiring haemodialysis, was consistent with the safety profile observed in the placebo‑controlled trials.

Tabulated summary of adverse reactions

The adverse reactions in Table 4 are listed below by system organ class and frequency. Frequencies are defined as follows: Very common (≥ 1/10); common (≥ 1/100 to < 1/10); uncommon (≥ 1/1,000 to < 1/100); rare (≥ 1/10,000 to < 1/1,000); not known (frequency cannot be estimated from the available data).

Table 4: Adverse reactions with Paxlovid

System organ class

Frequency category

Adverse reactions

Immune system disorders

Uncommon

Hypersensitivity*

Rare

Anaphylaxis*

Nervous system disorders

Common

Dysgeusia, headache

Vascular disorders

Uncommon

Hypertension*

Gastrointestinal disorders

Common

Diarrhoea, nausea*

Uncommon

Vomiting, abdominal pain*

Skin and subcutaneous tissue disorders

Rare

Toxic epidermal necrolysis*, Stevens‑Johnson syndrome*

General disorders and administration site conditions

Rare

Malaise*

* Adverse drug reaction (ADR) identified post-marketing.

Paediatric population

The safety and efficacy of Paxlovid in paediatric patients have not been established.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Coronavirus Yellow Card Reporting site at https://coronavirus-yellowcard.mhra.gov.uk/ or search for MHRA Yellow Card in the Google Play or Apple App Store.

4.9. Overdose

Treatment of overdose with Paxlovid should consist of general supportive measures including monitoring of vital signs and observation of the clinical status of the patient. There is no specific antidote for overdose with Paxlovid.

🇷🇴 Known in Romania as

Medicines sold in Romania with the same active substance: Cunoscut în România ca

  • PAXLOVID 150 mg+100 mg prescriptionNIRMATRELVIRUM+RITONAVIRUM · taken by mouth

Same active substance. The strength, the form and whether you need a prescription can differ. Always ask a pharmacist before you switch. Romanian medicines in the UK →

🇵🇱 Known in Poland as

Medicines sold in Poland with the same active substance: W Polsce znany jako

  • PaxlovidNirmatrelvirum + Ritonavirum · taken by mouth

Same active substance. The strength, the form and whether you need a prescription can differ. Always ask a pharmacist before you switch. Polish medicines in the UK →

💬 Ask about this leaflet

Ask anything about Paxlovid 150 mg/100 mg film-coated tablets. The assistant answers only from this leaflet — if the leaflet does not cover it, it will say so. It does not give medical advice.

Answers come from the patient leaflet published on the electronic medicines compendium (emc). They are not medical advice. Ask a pharmacist or your GP if you are unsure. For urgent help call NHS 111, or 999 in an emergency.

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