Foscarnet sodium

Intravenous
Cytomegaloviral retinitis in AIDS patients

Intravenous
Aciclovir-resistant mucocutaneous herpes simplex virus infection

Cytomegaloviral retinitis in AIDS patients:

CrCl (mL/kg/min)	Dosage
<0.4	Not recommended.
0.4-0.6	Induction: 21 mg/kg via infusion over 1 hour, every 8 hours. Maintenance: Same with induction dosage, to be given once daily.
0.6-0.8	Induction: 28 mg/kg via infusion over 1 hour, every 8 hours. Maintenance: Same with induction dosage, to be given once daily.
0.8-1.0	Induction: 35 mg/kg via infusion over 1 hour, every 8 hours. Maintenance: Same with induction dosage, to be given once daily.
1.0-1.2	Induction: 42 mg/kg via infusion over 1 hour, every 8 hours. Maintenance: Same with induction dosage, to be given once daily.
1.2-1.4	Induction: 49 mg/kg via infusion over 1 hour, every 8 hours. Maintenance: Same with induction dosage, to be given once daily.
1.4-1.6	Induction: 55 mg/kg via infusion over 1 hour, every 8 hours. Maintenance: Same with induction dosage, to be given once daily.
>1.6	Induction: 60 mg/kg via infusion over 1 hour, every 8 hours. Maintenance: Same with induction dosage, to be given once daily.

Aciclovir-resistant mucocutaneous herpes simplex virus infections:

CrCl (mL/kg/min)	Dosage
0.4-0.6	14 mg/kg via infusion over 1 hour, every 8 hours.
0.6-0.8	19 mg/kg via infusion over 1 hour, every 8 hours.
0.8-1.0	24 mg/kg via infusion over 1 hour, every 8 hours.
1.0-1.2	28 mg/kg via infusion over 1 hour, every 8 hours.
1.2-1.4	33 mg/kg via infusion over 1 hour, every 8 hours.
1.4-1.6	37 mg/kg via infusion over 1 hour, every 8 hours.
>1.6	40 mg/kg via infusion over 1 hour, every 8 hours.

Dilute with equal amount of dextrose in water 5% or NaCl 0.9% inj to provide a solution containing 12 mg/mL.

Lactation.

Patient with electrolyte imbalance, neurologic or cardiac abnormalities, heart failure, history or risk of QT prolongation, risk factors for seizures. Renal impairment. Pregnancy.

Significant: Electrolyte imbalance (e.g. hypokalaemia, hypocalcaemia, hypomagnesaemia, hyper/hypophosphataemia), anaemia, granulocytopaenia, QT prolongation, seizures, serious hypersensitivity reactions (e.g. anaphylactic shock, angioedema).
Blood and lymphatic system disorders: Thrombocytopenia, neutropenia, leucopenia, bone marrow suppression.
Eye disorders: Visual disturbance.
Gastrointestinal disorders: Diarrhoea, nausea, vomiting, abdominal pain.
General disorders and administration site conditions: Fever, weakness, asthenia, chills, malaise, fatigue.
Injury, poisoning and procedural complications: Injection site reactions.
Investigations: Blood creatinine increased, haemoglobin decreased, electrocardiogram abnormal, decreased creatinine clearance.
Metabolism and nutrition disorders: Decreased appetite.
Musculoskeletal and connective tissue disorders: Muscle spasm.
Nervous system disorders: Headache, dizziness, paraesthesia, hypoaesthesia, peripheral neuropathy, rigors/tremor.
Psychiatric disorders: Anxiety, depression, aggression, agitation.
Renal and urinary disorders: Nephrotoxicity.
Respiratory, thoracic and mediastinal disorders: Cough, dyspnoea.
Skin and subcutaneous tissue disorders: Rash, diaphoresis, pruritus.
Potentially Fatal: Renal impairment.

IV/Parenteral: C

This drug may cause dizziness, if affected, do not drive or operate machinery.

Monitor ECG, 24-hour creatinine clearance, electrolytes at baseline and periodically thereafter. Monitor complete blood count, electrolytes (e.g. Mg, Ca, K, phosphorus) twice weekly during induction stage and once weekly during maintenance therapy. Check hydration status before administration.

Symptoms: Seizures, renal impairment, paraesthesias, electrolyte disturbances. Management: Haemodialysis and hydration may be of benefit.

May enhance nephrotoxic effect with aminoglycosides, amphotericin B, ciclosporin, aciclovir, methotrexate and tacrolimus. Increased risk of QT prolongation with antiarrhythmic agents (e.g. quinidine, amiodarone, sotalol).

Description:
Mechanism of Action: Foscarnet sodium is a non-nucleoside pyrophoshate analogue which acts as a noncompetitive inihibitor of many viral RNA and DNA polymerases as well as HIV reverse transcriptase.
Pharmacokinetics:
Distribution: Volume of distribution: Approx 0.5 L/kg. Plasma protein binding: Approx 14% to 17%.
Excretion: Via urine (≤28% as unchanged drug). Elimination half-life: Approx 3 to 4 hours.

Source: National Center for Biotechnology Information. PubChem Database. Foscarnet sodium, CID=44561, https://pubchem.ncbi.nlm.nih.gov/compound/Foscarnet-sodium (accessed on Jan. 21, 2020)

Store between 20-25°C. Do not refrigerate.

Antivirals

J05AD01 - foscarnet ; Belongs to the class of phosphonic acid derivative antivirals. Used in the systemic treatment of viral infections.

Anon. Foscarnet. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 03/05/2018.

Buckingham R (ed). Foscarnet Sodium. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 03/05/2018.

Foscavir Injection (Astrazeneca LP). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 03/05/2018.

Joint Formulary Committee. Foscarnet Sodium. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 03/05/2018.