Fosamprenavir with other protease inhibitors

Based on the limited data with other protease inhibitors, the manufacturer of amprenavir also recommends it should not be given within 1 hour of antacids. The decrease in amprenavir levels seen when fosamprenavir is given with an antacid are not considered clinically relevant, and no fosamprenavir dose adjustments are likely to be neeessary. Greater decreases were seen with ranitidine, although the minimum levels were unehanged. The UK manufaeturer states that no fosamprenavir dose adjustment is needed with ranitidine or other H2-receptor antagonists however, the US manufacturer says the combination should be used with caution because fosamprenavir may be less effective. However, no interaction occurred with esomeprazole, and this, or other proton pump inhibitors may be given at the same time as fosamprenavir. 

Fosamprenavir is a protease inhibitor. Fosamprenavir is a prodrug of amprenavir that inhibits HIV protease, the enzyme required to form functional proteins in HIV-infected patients. It is indicated in the treatment of HIV infections in combination with other antiretroviral agents. 

A number of other protease inhibitors (Fig. 23.16) have been developed in the last few years with the aim of improving pharmacokinetic profile. One of the first of these was amprenavir, which does not contain peptide bonds which slows down its clearance from the body. Its pharmokinetics are further improved when it is administered as its phosphate prodmg fosamprenavir. Lopinavir was also developed to give improved pharmacokinetics. Its effectiveness is improved by co-administration with... 

Fosamprenavir calcium has been approved for the treatment of HIV in adults when used in combination with other anti-HIV drugs. It is a prodrug that, on hydrolysis by serum phosphatases, gives rise to amprenavir, which is a peptidomimetic transition-state inhibitor that targets HIV-1 protease and reduces the viral replication and, thus, the infectiousness of HIV-1. It is commonly administered in combination with RT inhibitors to produce excellent efficacy in patients with AIDS. The drug is administered as two 700 mg tablets twice daily or, in combination with ritonavir, can be given as two 700 mg tables once daily or one 700 mg tablet twice daily. As a result, formaprenavir lowers the pill burden in patients with AIDS. 

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