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Fosamprenavir
- indication:Indicated in combination with other antiretroviral agents for the treatment of human immunodeficiency virus (HIV-1) infection, as well as postexposure prophylaxis of HIV infection in individuals who have had occupational or nonoccupational exposure to potentially infectious body fluids of a person known to be infected with HIV when that exposure represents a substantial risk for HIV transmission. The use of fosamprenavir is pending revision due to a potential association between the drug and myocardial infarction and dyslipidemia in HIV infected adults.
- pharmacologypharmacology:
- mechanism: Fosamprenavir is a prodrug that is rapidly hydrolyzed to amprenavir by cellular phosphatases in the gut epithelium as it is absorbed. Amprenavir is an inhibitor of HIV-1 protease. During HIV replication, HIV protease cleaves viral polypeptide products of the Gag and Gag-Pol genes to form structural proteins of the virion core and essential viral enzymes. Amprenavir interferes with this process by binding to the active site of HIV-1 protease, thereby preventing the processing of viral Gag and Gag-Pol polyprotein precursors, resulting in the formation of immature non-infectious viral particles.
- toxicity:
- absorprion: The absolute oral bioavailability of amprenavir after administration of fosamprenavir in humans has not been established. After administration of a single 1,400 mg dose in the fasted state, fosamprenavir oral suspension (50 mg/mL) and fosamprenavir tablets (700 mg) provided similar amprenavir exposures (AUC), however, the C<sub>max</sub> of amprenavir after administration of the suspension formulation was 14.5 % higher compared with the tablet.
- halflife: The plasma elimination half-life of amprenavir (the active metabolite) is approximately 7.7 hours.
- roouteelimination: Excretion of unchanged amprenavir in urine and feces is minimal. The renal elimination of unchanged amprenavir represents approximately 1% of the administered dose; therefore, renal impairment is not expected to significantly impact the elimination of amprenavir. Amprenavir, the active metabolite of fosamprenavir, is metabolized in the liver by the cytochrome P450 enzyme system.
- volumedistribution:
- clearance: