Cidofovir Trimethoprim

Zidovudine (AZT) Retrovir 100 mg capsule, 300 mg tablets 10 mg/ml injectable 50 mg/5 ml syrup Trimethoprim/sulfamethoxazole, trimethoprim, cidofovir... 

Items 6-7 A patient with AIDS has a CD4 count of 45/ xL. He is being maintained on a three-drug regimen of indinavir, zalcitabine, and zidovudine. For prophylaxis against opportunistic infections, he is also receiving cidofovir, fluconazole, rifabutin, and trimethoprim-sulfamethoxazole. 

The modest decreases in trimethoprim and sulfamethoxazole levels, and moderate increases in didanosine levels caused by cidofovir are considered unlikely to be clinically relevant because of the infrequent dosing schedule of cidofovir/probenecid. No dose adjustments are considered necessary. ... 

Cidofovir with probenecid modestly decreased levels of trimethoprim and sulfamethoxazole (co-trimoxazole), and caused moderate increases in didanosine levels, but did not alter fluconazole pharmacokinetics. None of these drugs altered cidofovir pharmacokinetics. 

In a study, 6 HIV-positive subjects were given co-trimoxazole 960 mg daily with a single 3-mg/kg dose of cidofovir with probenecid given on day 7. The AUC and maximum plasma concentrations of both trimethoprim and sulfamethoxazole were decreased by about 30% and renal clearance was significantly increased. The pharmacokinetics of cidofovir were not affected. ... 

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