4.1. Therapeutic indications

Foscavir is indicated for induction and maintenance therapy of cytomegalovirus (CMV) retinitis in patients with AIDS.

Foscavir is also indicated for the treatment of mucocutaneous Herpes Simplex Virus (HSV) infections, clinically unresponsive to aciclovir in immunocompromised patients. The safety and efficacy of Foscavir for the treatment of other HSV infections (e.g. retinitis, encephalitis); congenital or neonatal disease; or HSV in immunocompetent individuals has not been established.

The diagnosis of aciclovir unresponsiveness can be made either clinically by treatment with intravenous aciclovir (5–10 mg/kg t.i.d) for 10 days without response or by in vitro testing.

Foscavir is not recommended for treatment of CMV infections other than retinitis or HSV or for use in non-AIDS or non-immunocompromised patients.

4.2. Posology and method of administration

Method of administration: Foscarnet should be administered by the intravenous route only, either by a central venous line or in a peripheral vein.

When peripheral veins are used, the solution of foscarnet 24 mg/ml must be diluted. Individually dispensed doses of foscarnet should be aseptically transferred and diluted with equal parts of 0.9% sodium chloride (9 mg/ml) or 5% dextrose (50 mg/ml) by the hospital pharmacy. The diluted solutions should be used as soon as possible after preparation but can be stored for up to 24 hours if kept refrigerated.

The solution of foscarnet 24 mg/ml may be given without dilution via a central vein.

Adults: Induction therapy for CMV retinitis: Foscavir is administered over 2–3 weeks depending on the clinical response, as intermittent infusions every 8 hours at a dose of 60 mg/kg in patients with normal renal function. Dosage must be individualised for patient's renal function (see dosing chart below). The infusion time should not be shorter than 1 hour.

Maintenance therapy: For maintenance therapy, following induction therapy of CMV retinitis, Foscavir is administered seven days a week as long as therapy is considered appropriate. In patients with normal renal function, it is recommended to initiate therapy at 60 mg/kg. Increase to a dose of 90–120 mg/kg may then be considered in patients tolerating the initial dose level and/or those with progressive retinitis. A number of patients have received 90 mg/kg over a 2 hour period as a starting dose for maintenance therapy. Dosage must be reduced in patients with renal insufficiency (see dosage chart at end of dosage section).

Patients who experience progression of retinitis while receiving maintenance therapy may be re-treated with the induction regimen.

Induction therapy of mucocutaneous HSV infections unresponsive to aciclovir: Foscavir is administered for 2–3 weeks or until healing of lesions, as intermittent infusions at a dose of 40 mg/kg over one hour every 8 hours in patients with normal renal function. Dosage must be individualised for patients renal function (see dosing chart below). The infusion time should not be shorter than 1 hour.

Efficacy of Foscavir maintenance therapy following induction therapy of aciclovir unresponsive HSV infections has not been established.

Caution: Do not administer Foscavir by rapid intravenous injection.

Table 1 Foscavir Dosing Chart

Induction Therapy

Creatinine Clearance

(ml/kg/min)

CMV

Every 8 Hours (mg/kg)

HSV

Every 8 Hours (mg/kg)

> 1.6

60

40

1.6–1.4

55

37

1.4–1.2

49

33

1.2–1.0

42

28

1.0–0.8

35

24

0.8–0.6

28

19

0.6–0.4

21

14

< 0.4

Treatment not recommended

CMV Maintenance Therapy

Creatinine Clearance

(ml/kg/min)

One Infusion Dose

(mg/kg/day in not less than one hour)

> 1.6

60*

1.6–1.4

55

1.4–1.2

49

1.2–1.0

42

1.0–0.8

35

0.8–0.6

28

0.6–0.4

21

< 0.4

Treatment not recommended

*A number of patients have received 90 mg/kg as a starting dose for maintenance therapy.

Foscavir is not recommended in patients undergoing haemodialysis since dosage guidelines have not been established.

Hydration: Renal toxicity of Foscavir can be reduced by adequate hydration of the patient. It is recommended to establish diuresis by hydration with 0.5–1.0 litre of normal saline at each infusion. In compliant patients, oral hydration with similar hydration regimens has been used. Clinically dehydrated patients should have their condition corrected before initiating Foscavir therapy.

Elderly: As for adults.

Paediatric population: The safety and efficacy of foscarnet in children have not been established. Please refer to sections 4.4 and 5.3.

Renal or hepatic insufficiency: The dose must be reduced in patients with renal insufficiency according to the creatinine clearance level as described in the table above. Dose adjustment is not required in patients with hepatic insufficiency.

4.3. Contraindications

Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.

4.4. Special warnings and precautions for use

Foscavir should be used with caution in patients with reduced renal function. Since renal function impairment may occur at any time during Foscavir administration, serum creatinine should be monitored every second day during induction therapy and once weekly during maintenance therapy and appropriate dose adjustments should be performed according to renal function. Adequate hydration should be maintained in all patients (see section 4.2). The renal function of patients with renal disease or receiving concomitant treatment with other nephrotoxic medicinal products must be closely monitored (see section 4.5).

This medicinal product contains 1.38 g of sodium per 250 ml bottle, equivalent to 69% of the WHO recommended maximum daily intake of 2 g sodium for an adult.

The maximum recommended daily dose of this product is 12 g of Foscavir per day (180 mg/kg/day in average 70 kg male), which is equivalent to 138% of the WHO recommended maximum daily dietary intake for sodium.

Foscavir is considered high in sodium. This should be particularly taken into account for those on a low sodium diet. Its use should be avoided when a saline load cannot be tolerated (e.g. in cardiomyopathy).

Due to Foscavir's propensity to chelate bivalent metal ions, such as calcium, Foscavir administration may be associated with an acute decrease of ionised serum calcium proportional to the rate of Foscavir infusion, which may not be reflected in total serum calcium levels. The electrolytes, especially calcium and magnesium, should be assessed prior to and during Foscavir therapy and deficiencies corrected.

Foscarnet has been associated with cases of prolongation of QT interval and more rarely with cases of torsade de pointes (see section 4.8). Patients with known existing prolongation of cardiac conduction intervals, particularly QTc, patients with significant electrolyte disturbances (hypokalaemia, hypomagnesaemia), bradycardia, as well as patients with underlying cardiac diseases such as congestive heart failure or who are taking medications known to prolong the QT interval should be carefully monitored due to increased risk of ventricular arrhythmia. Patients should be advised to promptly report any cardiac symptoms.

Foscavir is deposited in teeth, bone and cartilage. Animal data show that deposition is greater in young animals. The safety of Foscavir and its effect on skeletal development have not been investigated in children. Please refer to section 5.3.

Seizures, related to alterations in plasma minerals and electrolytes, have been associated with Foscavir treatment. Cases of status epilepticus have been reported. Therefore, patients must be carefully monitored for such changes and their potential sequelae. Mineral and electrolyte supplementation may be required.

Foscavir is excreted in high concentrations in the urine and may be associated with significant genital irritation and/or ulceration. To prevent irritation and ulceration, close attention to personal hygiene is recommended and cleaning of the genital area after each micturition is recommended.

Should patients experience extremity paraesthesia or nausea, it is recommended to reduce the speed of infusion.

When diuretics are indicated, thiazides are recommended.

Development of resistance: If the administration of Foscavir does not lead to a therapeutic response or leads to a worsened condition after an initial response, this may result from a reduced sensitivity of viruses towards foscarnet. In this case, termination of Foscavir therapy and a change to an appropriate other medicinal product should be considered.

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

Since Foscavir can impair renal function, additive toxicity may occur when used in combination with other nephrotoxic drugs such as aminoglycosides, amphotericin B, ciclosporin A, aciclovir, methotrexate and tacrolimus. Moreover, since Foscavir can reduce serum levels of ionised calcium, extreme caution is advised when used concurrently with other drugs known to influence serum calcium levels, like i.v. pentamidine. Renal impairment and symptomatic hypocalcaemia (Trousseau's and Chvostek's signs) have been observed during concurrent treatment with Foscavir and i.v. pentamidine. Abnormal renal function has been reported in connection with the use of Foscavir in combination with ritonavir and/or saquinavir.

Due to the potential increased risk of QT prolongation and torsade de pointes, Foscavir should be used with caution with drugs known to prolong QT interval, notably class IA (e.g. quinidine) and III (e.g. amiodarone, sotalol), antiarrhythmic agents or neuroleptic drugs. Close cardiac monitoring should be performed in cases of co-administration.

There is no pharmacokinetic interaction with zidovudine (AZT), ganciclovir, didanosine (ddI), zalcitabine (ddC) or probenecid.

Pharmaceutical interactions (incompatibilities for infusion) are described in section 6.2.

4.6. Fertility, pregnancy and lactation

Fertility

There are no data available regarding the influence of Foscavir on fertility.

No effects on fertility were observed in animal studies (see section 5.3).

Women of childbearing potential / contraception in males and females

Women capable of childbearing should use effective contraception methods during Foscavir therapy.

Men treated with Foscavir should not father a child during or up to 6 months after therapy.

Pregnancy

There are no or limited amount of data from the use of foscarnet in pregnant women.

Animal studies are insufficient with respect to reproductive toxicity (see section 5.3).

Foscavir is not recommended during pregnancy.

Lactation

There is insufficient information on the excretion of foscarnet in human milk.

Available pharmacodynamic/toxicological data in animals have shown excretion of foscarnet in milk (for details see section 5.3).

A risk to the newborns/infants cannot be excluded.

Foscavir should not be used during breast-feeding. .

A decision must be made whether to discontinue breast-feeding or to discontinue/abstain from Foscavir therapy taking into account the benefit of breast feeding for the child and the benefit of therapy for the woman.

4.7. Effects on ability to drive and use machines

Foscavir has moderate influence on the ability to drive and use machines. Due to the disease itself and possible undesirable effects of Foscavir (such as dizziness and convulsions, see section 4.8), the ability to drive and use machines can be impaired. The physician is advised to discuss this issue with the patient, and based upon the condition of the disease and the tolerance of medication, give a recommendation in the individual case.

4.8. Undesirable effects

The majority of patients who receive Foscavir are severely immuno-compromised and suffering from serious viral infections. Patients' physical status, the severity of the underlying disease, other infections and concurrent therapies contribute to adverse events observed during use of Foscavir.

The undesirable effects reported with Foscavir during clinical trials and post-marketing surveillance are shown in the table below. They are listed by System-Organ Class (SOC) and in order of frequency, using the following convention: 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); very rare (<1/10,000); not known (cannot be estimated from the available data).

Please note that in these clinical trials, hydration and attention to electrolyte balance was not consistently given; the frequency of some adverse events will be lower when current recommendations are followed (see sections 4.2 and 4.4).

Table 2 Frequency of adverse events

SOC

Frequency

Event

Blood and lymphatic system disorders

Very common

Granulocytopenia, anaemia

Common

Leukopenia, thrombocytopenia, neutropenia

Uncommon

Pancytopenia

Immune system disorders

Common

Sepsis

Not known

Hypersensitivity (including anaphylactic reactions), anaphylactoid reactions

Endocrine disorders

Not known

Diabetes insipidus

Metabolism and nutrition disorders

Very common

Decreased appetite, hypokalaemia, hypomagnesaemia, hypocalcaemia

Common

Hyperphosphataemia, hyponatraemia, hypophosphataemia, blood alkaline phosphatase increased, blood lactate dehydrogenase increased, hypercalcaemia, dehydration

Uncommon

Acidosis

Not known

Hypernatraemia

Psychiatric disorders

Common

Aggression, agitation, anxiety, confusional state, depression, nervousness

Nervous system disorders

Very common

Dizziness, headache, paraesthesia

Common

Coordination abnormal, convulsion, hypoaesthesia, muscle contractions involuntary, neuropathy peripheral, tremor

Cardiac disorders

Common

Palpitations, tachycardia

Not known

Electrocardiogram QT prolonged, ventricular arrhythmia, torsade de pointes

Vascular disorders

Common

Hypertension, hypotension, thrombophlebitisa

Gastrointestinal disorders

Very common

Diarrhoea, nausea, vomiting

Common

Abdominal pain, constipation, dyspepsia, pancreatitis, gastrointestinal haemorrhage

Not known

Oesophageal ulceration

Hepatobiliary disorders

Common

Hepatic function abnormal

Skin and subcutaneous disorders

Very common

Rash

Common

Pruritus

Uncommon

Urticaria, angioedema

Not known

Erythema multiforme, toxic epidermal necrolysis, Stevens Johnson syndromeb

Musculoskeletal and connective tissue disorders

Common

Myalgia

Not known

Muscular weakness, myopathy, myositis, rhabdomyolysis

Renal and urinary disorders

Common

Renal impairment, renal failure acute, dysuria, polyuria, proteinuria

Uncommon

Glomerulonephritis, nephrotic syndrome

Not known

Renal pain, renal tubular acidosis, crystal nephropathy, haematuria

Reproductive system and breast disorders

Common

Genital discomfort and ulcerationc

General disorders and administration site conditions

Very common

Asthenia, chills, fatigue, pyrexia

Common

Malaise, oedema, chest paind, injection site pain, injection site inflammation

Not known

Extravasation

Investigations

Very common

Blood creatinine increased, haemoglobin decreased

Common

Creatinine renal clearance decreased, electrocardiogram abnormal, gamma-glutamyltransferase increased, alanine aminotransferase increased, aspartate aminotransferase increased, lipase increased

Uncommon

Amylase increased, blood creatine phosphokinase increased

a Thrombophlebitis in peripheral veins following infusion of undiluted foscarnet solution has been observed.

b Cases of vesiculobullous eruptions including erythema multiforme, toxic epidermal necrolysis, and Stevens Johnson syndrome have been reported. In most cases, patients were taking other medications that have been associated with toxic epidermal necrolysis or Stevens Johnson syndrome.

c Foscarnet is excreted in high concentrations in the urine and may be associated with significant irritation and ulceration in the genital area, particularly after prolonged therapy.

d Transient chest pain has been reported as part of infusion reactions to foscarnet.

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 has been reported during the use of Foscavir, the highest being some 20 times the recommended dose. Some of the cases were relative overdoses, in that the dose of drug used had not been promptly adjusted for a patient experiencing reduced renal function.

There are cases where it has been reported that no clinical sequelae were consequent on the overdose.

The pattern of adverse events reported in association with an overdose of Foscavir is in accordance with the known adverse event profile of the drug.

Haemodialysis increases Foscavir elimination and may be of benefit in relevant cases.