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.
Histergan 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 Diphenhydramine hydrochloride may still be available. Do not stop your treatment — ask your pharmacist or GP what to use instead.
What it is and what it is used for
for? Histergan Tablets contain the following active ingredient: Diphenhydramine hydrochloride. Diphenhydramine hydrochloride is an antihistamine which works by blocking the body's response to histamine, which is an agent responsible for causing allergic responses such as hay fever, stings and rashes. Histamine is also involved in the brain's waking system so diphenhydramine hydrochloride can help alleviate temporary sleeplessness.
What you need to know before you take it
e Histergan Tablets Do not use Histergan Tablets: ££ if you are allergic to diphenhydramine hydrochloride or any of the ingredients listed in section 6 of this leaflet ££ if you have a peptic ulcer ££ if you have a blockage between your stomach and small intestine. Warnings and precautions Talk to your doctor or pharmacist before taking Histergan Tablets: ££ if you suffer from myasthenia gravis (abnormal muscle function) ££ if you suffer from seizures or have epilepsy ££ If you asthma, bronchitis or Chronic Obstructive Pulmonary Disease (COPD) ££ if you have narrow-angle glaucoma ££ if you have an enlarged prostate ££ if you have difficulty urinating ££ if you have moderate to severe liver or kidney problems ££ if you are elderly, particularly if you also suffer from confusion. This medicine is for short term use. It may not work as well if you use it continuously. If your symptoms persist, see your doctor for advice.
Other medicines and Histergan Tablets: Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines, including: ££ Other antihistamines including those used on your skin and in cough and cold medicines ££ Tranquillisers or anxiolytics (sedatives) used to treat anxiety e.g. diazepam ££ Hypnotics (e.g. nitrazepam) used to help you sleep better ££ Monoamine oxidase inhibitors (MAOIs) for depression (e.g. phenelzine) or if you have stopped taking an MOAI within the last two weeks ££ Metoprolol (a beta blocker) used to treat high blood pressure, angina, irregular heart beat or overactive thyroid ££ Venlafaxine used to treat depression ££ Anticholinergics which relax smooth muscles and are used for example in Parkinson's disease, irritable bowel syndrome and incontinence e.g. procyclidine, trihexyphenidyl, atropine, oxybutynin, fesoterodine ££ Tricyclic antidepressants (e.g. imipramine, amitriptyline). Histergan Tablets with alcohol: While taking Histergan Tablets avoid alcoholic drink. Pregnancy and breast-feeding: Do not take Histergan Tablets if you are pregnant or breast-feeding. Driving and using machines: This medicine causes drowsiness and sedation and may also cause dizziness, blurred vision, disturbance in attention and slower reaction times. Do not drive or operate machinery while you are affected in this way. Histergan Tablets contain lactose and sucrose: If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicinal product.
How to take it
Histergan Tablets Always use this medicine exactly as described in this leaflet or as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure. The recommended dose is: For the treatment of hay fever, stings, rashes and other minor allergies: Adults and children over 12 years: 1 or 2 tablets three or four times a day or as prescribed by a doctor. Not recommended for children under 12 years of age. For use as a temporary sleep aid: Adults: 1 or 2 tablets to be taken at bedtime or after retiring when sleep is not readily achieved. Do not take a repeat dose in the same night. Not recommended as a sleep aid in children under 16 years of age. If you take more Histergan Tablets than you should: Seek medical attention as soon as possible. When seeking medical advice you should, if possible, take the medicine and this leaflet with you provided it doesn't cause a delay. 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. If any of the following occur STOP TAKING the tablets IMMEDIATELY and contact your doctor, as these may be signs of an allergic reaction: ££ Difficulty breathing or shortness of breath, swelling of the face, mouth or throat ££ Rash, hive (itchy, raised red weals). If you notice any of the following effects tell your doctor straightaway: ££ Faster heartbeat, irregular heartbeat ££ Fits, difficulty making or controlling movements. Tell your doctor, pharmacist or nurse if you suffer from any of the following other effects: Common effects (may affect up to 1 in 10 people): ££ Sedation, drowsiness, dizziness, unsteadiness, disturbance, inattention ££ Dry mouth ££ Fatigue. Other effects (frequency not known – cannot be estimated from the data available): ££ Palpitations (feeling your heartbeat) ££ Headache, tingling or numbness (pins and needles) ££ Depression, sleep disturbances ££ Confusion, excitation e.g. increased energy, restlessness, nervousness (the elderly are more likely to experience these effects) ££ Difficulty urinating or inability to pass urine
££ Thicker bronchial mucus ££ Blurred vision ££ Feeling or being sick, stomach problems ££ Muscle twitching. Reporting of side effects If you get any side effects, talk to your doctor or pharmacist or nurse. This includes any possible side effects not listed in this leaflet. You can also report
Possible side effects
directly via the Yellow Card Scheme at www.mhra.gov.uk/yellowcard 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.
How to store it
Histergan Tablets Keep this medicine out of the sight and reach of children. Store below 25°C. Do not use this medicine after the expiry date which is stated on the carton and blister pack. The expiry date refers to the last day of that month. 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.
Contents of the pack and other information
What Histergan Tablets contain: The active substance is diphenhydramine hydrochloride, 25mg. The other ingredients are: lactose, corn starch, povidone, magnesium stearate, Opaseal (polyvinyl acetate phthalate, ethyl acetate and stearic acid), sucrose, calcium carbonate, talc, acacia, titanium dioxide E171, Opalux Pink AS 1537 (E127 erythrosine), Opaglos 6000 (carnauba wax, beeswax), silicone fluid. What Histergan Tablets look like and the contents of the pack: Histergan Tablets are pink, sugar coated, tablets and are supplied in packs of 8, 16 or 20 tablets. Not all pack sizes may be marketed. Marketing Authorisation Holder and Manufacturer: The marketing authorisation holder is: Norma Chemicals Ltd., 51-53 Stert Street, Abingdon, Oxfordshire, OX14 3JF, UK. The EEA site of batch release is: Surepharm Services Ltd., Bretby Business Park, Burton upon Trent, DE15 0YZ, UK. or Wasdell Packaging Ltd., Euroway Industrial Estate, Blagrove, Swindon, Wiltshire, SN5 8YW, UK This Leaflet was last revised in September 2017 PL00386/5008R
Frequently asked questions about Histergan Tablets
How do I take Histergan Tablets?
Histergan Tablets comes as tablet. 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 Histergan Tablets?
The active substance in Histergan Tablets is diphenhydramine hydrochloride.
Where does this information come from?
This leaflet reproduces the patient information leaflet approved for Histergan 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 Histergan 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.
- Source: electronic medicines compendium (emc), Datapharm
- Active substance: diphenhydramine hydrochloride
- Official document: view the original leaflet on emc →
⚕For healthcare professionals — Summary of Product Characteristics (SmPC)Full SmPC: dosage, interactions, contraindications, warnings+
4.1. Therapeutic indications
As an antihistamine: Treatment of allergic conditions e.g. hay fever, vasomotor rhinitis, stings, urticaria, angioneurotic oedema, drug sensitivity, contact dermatitis and photosensitivity.
As a sleep aid: As a short term hypnotic.
4.2. Posology and method of administration
As an antihistamine:
Adults and Children over 12 years: 1 or 2 tablets three or four times per day. In severe or chronic conditions this may be increased at the discretion of a doctor, but not to exceed 300mg in any 24 hour period.
Paediatric Population:
Not recommended for children under the age of 12.
Elderly: As for adults, use cautiously, reduce dose if required.
As a sleep aid:
Adults: 1 or 2 tablets at bedtime, or after retiring when sleep is not readily achieved
Paediatric Population:
Not recommended for children under the age of 16
Elderly: As for adults, use cautiously, reduce dose if required.
4.3. Contraindications
Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.
Contraindicated for use in patients with the following conditions: stenosing peptic ulcer, pyloroduodenal obstruction.
When used as a sleep aid: Sedation of children under the age of 16 should only be under medical direction, consequently use as a sedative in this age group is contraindicated.
4.4. Special warnings and precautions for use
Diphenhydramine should be used with caution in patients with myasthenia gravis,epilepsy or seizure disorders, prostatic hypertrophy, urinary retention, narrow-angle glaucoma, asthma, bronchitis and chronic obstructive pulmonary disease (COPD), moderate to severe hepatic impairment and moderate to severe renal impairment.
Tolerance may develop with continuous use. Seek medical advice if sleeplessness persists, as insomnia may be a symptom of a serious underlying medical illness.
May increase the effects of alcohol, therefore alcohol should be avoided. Avoid use of other antihistamine-containing preparations, including topical antihistamines and cough and cold medicines.
Use with caution in the elderly, who are more likely to experience side-effects. Avoid use in elderly patients with confusion.
Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.
Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
4.5. Interaction with other medicinal products and other forms of interaction
Diphenhydramine may potentiate the sedative effects of alcohol and other CNS depressants (e.g. tranquillizers, hypnotics and anxiolytics).
Monoamine oxidase inhibitors (MAOIs) prolong and intensify the anticholinergic effects of diphenhydramine. The product should be used with caution with MAOIs or within 2 weeks of stopping an MAOI.
As diphenhydramine has some antimuscarinic activity, the effects of some anticholinergic drugs (e.g. atropine, tricyclic antidepressants) may be potentiated therefore medical advice should be sought before taking diphenhydramine with such medicines.
Diphenhydramine is an inhibitor of the cytochrome p450 isoenzyme CYP2D6. Therefore, there may be a potential for interaction with drugs which are primarily metabolised by CYP2D6, such as metoprolol and venlafaxine.
Diphenhydramine should not be used in patients receiving any of the above drugs unless directed by a doctor
4.6. Fertility, pregnancy and lactation
Pregnancy
Diphenhydramine crosses the placenta. Because animal reproduction studies are not always predictive of human response and since there is inadequate experience with use of diphenhydramine in pregnant women, the potential risk for humans is unknown. Use of sedating antihistamines during the third trimester may result in reactions in the newborn or premature neonates. This drug is not recommended during pregnancy. Consult a doctor before use.
Lactation
Diphenhydramine has been detected in breast milk, but the effect of this on breastfed infants is unknown. Diphenhydramine is not recommended for use during lactation. Consult a doctor before use.
4.7. Effects on ability to drive and use machines
Diphenhydramine is a hypnotic and will produce drowsiness or sedation soon after the dose has been taken. It may also cause dizziness, blurred vision, cognitive and psychomotor impairment. These can seriously affect the patient's ability to drive and use machines. If affected, do not drive or operate machinery.
4.8. Undesirable effects
Specific estimation of the frequency of adverse events for OTC products is inherently difficult (particularly numerator data). Adverse reactions which have been observed in clinical trials and which are considered to be common (occurring in >1/100 to <1/10) or very common (occurring in >1/10) are listed below by MedDRA System Organ Class. The frequency of other adverse reactions identified during postmarketing use is unknown, but these reactions are likely to be uncommon (occurring in >1/1,000 to <1/100) or rare (occurring in <1/1000).
System Organ Class
Very Common
(≥1/10)
Common
≥1/100, < 1/10
Uncommon
≥1/1,000, <1/100
Rare
≥1/10,000, <1/1000
Very Rare
<1/10,000
Not known (cannot be estimated from available data)
Cardiac Disorders
tachycardia, palpitations, arrhythmias
Eye Disorders
blurred vision
General disorders and administration site conditions:
fatigue
Gastrointestinal Disorders
dry mouth
gastrointestinal disturbance including nausea, vomiting
Immune System Disorders
hypersensitivity reactions including rash, urticaria, dyspnoea and angioedema
Musculoskeletal and connective tissue Disorders
muscle twitching
Nervous System Disorders
sedation, drowsiness, disturbance in attention, unsteadiness, dizziness
convulsions, headache, paraesthesia, dyskinesias
Psychiatric Disorders
confusion, paradoxical excitation (e.g. increased energy, restlessness, nervousness), depression, sleep disturbances
* The elderly are more prone to confusion and paradoxical excitation.
Renal and urinary disorders
urinary difficulty, urinary retention
Respiratory, thoracic and mediastinal disorders
thickening of bronchial secretions
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 Yellow Card Scheme, website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.
4.9. Overdose
Overdose is likely to result in effects similar to those listed under adverse reactions. Additional symptoms may include mydriasis, fever, flushing, agitation, tremor, dystonic reactions, hallucinations and ECG changes. Large overdose may cause rhabdomyolysis, convulsions, delirium, toxic psychosis, arrhythmias, coma and cardiovascular collapse.
Treatment should be supportive and directed towards specific symptoms. Convulsions and marked CNS stimulation should be treated with parenteral diazepam
🇷🇴 Known in Romania as
Medicines sold in Romania with the same active substance: Cunoscut în România ca
- CALMABEN 50 mg prescriptionDIPHENHYDRAMINUM · 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
- NodisenDiphenhydramini hydrochloridum · taken by mouth
- LuminastilDiphenhydramini hydrochloridum · 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 Histergan 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.