For the treatment of HIV-1 infection in combination with other antiretroviral agents.
Amprenavir inhibits the HIV viral proteinase enzyme which prevents cleavage of the gag-pol polyprotein, resulting in noninfectious, immature viral particles.
Rapidly absorbed after oral administration in HIV-1-infected patients with a time to peak concentration (T<sub>max</sub>) typically between 1 and 2 hours after a single oral dose. The absolute oral bioavailability of amprenavir in humans has not been established.
7.1-10.6 hours
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.
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.
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.
The plasma elimination half-life of amprenavir (the active metabolite) is approximately 7.7 hours.
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.