The antiviral drug foscarnet is used to treat CMV retinitis in the patient with AIDS. It’s also used to treat acyclovir-resistant HSV infections in the immunocompromised patient.
Foscarnet is poorly bound to plasma proteins. In patients with normal kidney function, the majority of foscarnet is excreted un-changed in urine.
Foscarnet prevents viral replication by selectively inhibiting DNA polymerase.
Foscarnet’s primary therapeutic use is treating CMV retinitis in the patient with AIDS. It’s also used in combination therapy with gan-ciclovir for the patient who has relapsed with either drug.
Foscarnet has few drug interactions.
§ Foscarnet and pentamidine together increase the risk of hypocalcemia (low blood calcium levels) and toxicity to the kid-neys.
§ The use of foscarnet and other drugs that alter serum calcium levels may result in hypocalcemia.
§ Foscarnet given with amiodarone increases the risk of car-diotoxicity and QT prolongation.
§ The risk of kidney impairment increases when drugs toxic to the kidneys, such as amphotericin B and aminoglycosides, are tak-en with foscarnet. Because of the risk of kidney toxicity, the pa-tient should be aggressively hydrated during treatment. (See Ad-verse reactions to foscarnet.)