Foscarnet
Common Brand Names: Foscavir
Therapeutic Class: Antiviral agent
Common Injectable Dosage Forms:
Solution for Injection: 24 mg/mL (250 mL, 500 mL)
Dosage Ranges:
Induction in cytomegalovirus (CMV) retinitis: 60 mg/kg/dose every 8 hours or 90 mg/kg every 12 hours for 14-21 days. Maintenance dose is 90-120 mg/kg/day as a single infusion.
Herpes Simplex (Acyclovir-resistant): 40 mg/kg/dose every 12 hours for 14-21 days.
Administration and Stability: Rate of infusion should not exceed 1 mg/kg/minute. Hydration with 750-1000 mL of NS or D5W prior to infusion is recommended. Peripheral line infusion requires dilution to maximum concentration of 12 mg/mL in NS or D5W. Central line infusion require no further dilution for infusion. Foscarnet is a hazardous agent and required appropriate precautions for handling and disposal. pH 7.4
Pharmacology/Pharmacokinetics: Foscarnet is a pyrophosphate analogue that acts as a noncompetitive inhibitor of many viral RNA and DNA polymerases, as well as HIV reverse transcriptase. Foscarnet is considered to a virostatic agent. Elimination half-life is 3 hours. Up to 28% of drug may be deposited in bone.
Drug and Lab Interactions: Concurrent use of fluoroquinolones with foscarnet increases seizure potential. Nephrotoxic drugs (amphotericin B, aminoglycosides, etc.) should be avoided. Protease inhibitors are associated with increased renal impairment when used concurrently. QT prolonging agents may enhance the adverse/toxic effects of foscarnet.
Contraindications/Precautions: Contraindicated in patients with a hypersensitivity to foscarnet. Discontinue therapy in patients with CrCl <0.4 mL/min/kg. Pregnancy Category C.
Monitoring Parameters: CrCl, CBC, electrolytes, hydration status
Adverse Effects: Possible side effects include fever, headache, hypokalemia, hypocalcemia, hypomagnesemia, hypophosphatemia, nausea, vomiting, diarrhea, anemia, and granulocytopenia. Foscarnet may also alter creatinine clearance/renal function.
Common Clinical Applications: Useful in the treatment of herpes virus infections thought to be acyclovir-resistant (HSV, VZV) or ganciclovir-resistant (CMV) strains. Also used in treatment of CMV retinitis in AIDS patients.