Foscarnet

Indications

Foscarnet is used for: Cytomegaloviral retinitis, in AIDS patients, Aciclovir-resistant mucocutaneous, herpes simplex virus infection

Adult Dose

Intravenous Cytomegaloviral retinitis in AIDS patients Adult: Induction: 60 mg/kg given via infusion over 1 hour, every 8 hours for 2-3 weeks. Maintenance: 60 mg/kg once daily, increase to 90-120 mg/kg once daily if tolerated. If progression occurs, re-treat with induction regimen. Aciclovir-resistant mucocutaneous herpes simplex virus infection Adult: In immunocompromised patients: 40 mg/kg via infusion over 1 hour, every 8 hours for 2-3 weeks or until lesions heal.

Child Dose

<18 years old: Safety and efficacy not established

Renal Dose

Administration

IV Preparation Should be diluted in D5W or NS & transferred to PVC containers For peripheral line administration, dilute to 12 mg/mL with D5W or NS For central line administration, may administer undiluted IV Administration Use an infusion pump, not exceeding 1 mg/kg/min Adult induction doses of 60 mg/kg are administered over a minimum 1 hr Adult maintenance doses of 90-120 mg are infused over 2 hr

Contra Indications

Hypersensitivity

Precautions

Caution with renal impairment Do not administer by rapid or bolus IV injection; use infusion pump May be associated with changes in serum electrolytes changes including hypocalcemia, hypo- or hyperphosphatemia, hypomagnesemia, or hypokalemia Serious acute hypersensitivity reactions (e.g., anaphylactic shock, urticaria, angioedema) reported; if such acute reactions occur, discontinue therapy; and institute appropriate medical therapy immediately Cases of status epilepticus reported; several cases of seizures associated with death; electrolyte abnormalities may increase risk of seizures

Pregnancy-Lactation

Pregnancy Category: C Lactation: not known if excreted in breast milk, do not nurse

Interactions

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).

Adverse Effects

Side effects of Foscarnet : >10% Fever (65%) Nausea (47%) Anemia (33%) Vomiting (33%) Diarrhea (30%) Abnormal renal function/decreased CrCl (27%) Headache (26%) Seizures (10%) 1-10% Fatigue Depression Confusion Anxiety Dizziness Hypoesthesia Malaise Rash Electrolyte imbalance (especially potassium, calcium, magnesium, and phosphorus) Leukopenia Neutropenia

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.