Fosamprenavir

Absorption

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 Cmax of amprenavir after administration of the suspension formulation was 14.5 % higher compared with the tablet.

The Uses of Fosamprenavir

Antiviral (HIV protease inhibitor).

Indications

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.

Background

Fosamprenavir is a prodrug of amprenavir, an inhibitor of human immunodeficiency virus (HIV) protease.

Definition

ChEBI: A sulfonamide with a structure based on that of sulfanilamide substituted on the sulfonamide nitrogen by a (2R,3S)-4-phenyl-2-(phosphonooxy)-3-({[(3S)-tetrahydrofuran-3-yloxy]carbonyl}amino)butyl group. It is a pro-drug of the HIV protease inhibitor and antiretroviral drug amprenavir.

Pharmacokinetics

Fosamprenavir is hydrolyzed by cellular phosphatases to the antiretroviral protease inhibitor amprenavir. This hydrolysis allows for the slow release of amprenavir, reducing the number of pills a patient must take.

Metabolism

In the gut epithelium during absorption, fosamprenavir is rapidly and almost completely hydrolyzed to amprenavir and inorganic phosphate prior to reaching the systemic circulation. Amprenavir is metabolized in the liver by the cytochrome P450 3A4 (CYP3A4) enzyme system.