Fosamprenavir Calcium

DescriptionFosamprenavir (calcium salt) is an orally bioavailable prodrug of the HIV-1 protease inhibitor amprenavir . Fosamprenavir has improved solubility compared with amprenavir, and its pharmacokinetics, either during fasting or with a low- or high-fat meal, suggest that it could be effective using fewer tablets and a less complex dosing schedule than other HIV treatments. Formulations containing fosamprenavir are used for adult and pediatric patients with HIV infection, especially as an initial antiretroviral therapy.

DescriptionFosamprenavir, a prodrug of the HIV protease inhibitor amprenavir, is indicated for the oral treatment of HIV infection in adults in combination with other antiretroviral agents. Although amprenavir has excellent antiviral potency and good tolerability, its watersolubility is poor (0.04 mg/ml). As a result, the formulation of the agent includes a high percentage of organic excipients to facilitate gastric dissolution, which limits the amount of active drug that can be formulated per capsule. Fosamprenavir is a highly soluble phosphate ester of amprenavir. It allows more convenient dosing and reduction in pill counts as compared to amprenavir. Fosamprenavir is readily prepared in two steps starting from a key intermediate used in the synthesis of amprenavir, by phosphorylating a hydroxyl group and subsequently reducing a p-nitrophenyl to a p-aminophenyl group. Fosamprenavir has little or no antiviral activity in vitro. After oral administration, it is rapidly and almost completely hydrolyzed by phosphatases in the gut epithelium to amprenavir prior to reaching systemic circulation. The time to reach peak plasma concentration of amprenavir is approximately 2.5 h and the plasma elimination half-life is approximately 7.7 h. Amprenavir is metabolized in the liver by CYP3A4 and ＞90% of the dose is excreted as metabolites in urine and feces. In most patients, fosamprenavir is administered at daily doses of 700–1400 mg in conjunction with ritonavir. Monotherapy with fosamprenavir is only recommended in antiretroviral therapy-nave patients and the dosing regimen is 1400 mg twice daily. The most common adverse events experienced with fosamprenavir are diarrhea, nausea, vomiting, headache and rash.