Foscarnet dosage

The most clinically significant adverse effect of foscarnet is renal impairment. Nephrotoxicity is most likely to occur during the second week of induction therapy but may occur at any time during induction or maintenance therapy. Serum creatinine levels may be elevated in up to 33 to 50% of patients this effect is usually reversible upon drug discontinuation. Dehydration, previous renal impairment, and concurrent administration of other nephrotoxic drugs increase the risk of renal toxicity. Infusion of fluids along with foscarnet decreases the likelihood of renal impairment to about 12%. Dosage adjustment is required for patients with renal insufficiency. 

Zidovudine should be used cautiously with any other agent that causes bone marrow suppression, such as interferon-a, trimethoprim-sulfamethoxazole, dap-sone, foscarnet, flucytosine, ganciclovir, and valganci-clovir. Probenecid and interferon-p inhibit the elimination of zidovudine therefore, a dosage reduction of zidovudine is necessary when the drugs are administered concurrently. Ribavirin inhibits the phosphorylation reactions that activate zidovudine, and zidovudine similarly inhibits the activation of stavudine thus, the coadministration of zidovudine with ribavirin or stavudine is contraindicated. 

In a non-randomized multicenter study of pre-emptive foscarnet sodium 90 mg/ kg/day in the prevention of human herpesvirus-6 (HHV-6) encephalitis in 21 allogeneic hemopoietic stem cell transplant recipients, the plasma HHV-6 DNA exceeded 5 x 10 copies/ml in eight patients [9 ]. The dosage was increased to 180 mg/ kg/day if the plasma HHV-6 DNA copy number increased to above 1 x 10 /ml or if... 

Acyclovir (30-60 mg/kg/day) can be given intravenously in three divided doses infused over a minimum of 1 hour for HSV pneumonitis. Two to 3 weeks of therapy usually suffices. Longer durations may be needed for patients with a poor response or those who are severely immunosuppressed. Foscarnet can be used to treat HSV pneumonitis in patients who have proven or suspected acyclovir-resistant HSV. Two to 3 weeks of intfavenous foscarnet at a dosage of 180 mg/kg/day divided in three daily doses should be adequate (70). 

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