Rifampicin Amprenavir

Amprenavir No Coadministration of amprenavir with rifampicin is not recommended because rifampicin markedly decreases concentrations of amprenavir... 

The adverse effects of amprenavir in patients treated with combination therapy included nausea, vomiting, diarrhea, epigastric pain, flatulence, paresthesia, headache, rash, and fatigue (4). The contribution of a single drug to the observed adverse effects is difficult to establish. Amprenavir inhibits CYP3A4 to a greater extent than saquinavir, and to a much lesser extent than ritonavir (5). Co-administration with rifampicin and rifabutin should be avoided. Those who take... 

Co-administration of amprenavir with rifampicin and rifabutin should be avoided (12). 

The use of rifampicin with the protease inhibitors indinavir, nelfinavir, and amprenavir is contraindicated. However, these agents can be used with rifabutin after appropriate dosage reduction. Failure to reduce the dosage of rifabutin can result in toxic manifestations, such arthralgia and uveitis. 

Rifampicin (rifampin) bioavaiiabiiity is increased by indinavir, but amprenavir has no effect. Rifampicin markedly reduces the bioavailability of amprenavir, atazanavir/ritonavir, indinavir, indinavir with ritonavir, iopinavir/ritonavir, nelfinavir and saquinavir, but oniy modestiy reduces that of ritonavir. The effects of rifampicin on iopinavir/ritonavir and saquinavir/ritona-vir can be overcome by increasing the protease inhibitor dose, but this appears to increase adverse effects (hepatotoxicity). 

Rifampicin (Rifampin). When 11 healthy subjects were given amprenavir 1.2 g twice daily with rifampicin 600 mg daily to for 4 days the pharmacokinetics of rifampicin were not affected, but the AUC of amprenavir was reduced by 82%. The maximum plasma level of amprenavir was also reduced by 70%, from 9.2 to 2.78 micrograms/mL. ... 

It is expeeted that concurrent use of fosamprenavir or fosamprenavir/ritonavir with rifampicin will also result in large decreases in plasma concentrations of amprenavir. 

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