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A study that evaluated dosage adjustments of the protease inhibitor (PI) Agenerase (amprenavir) capsules in HIV patients treated with efavirenz or nevirapine, antiretroviral (ART) agents known to affect the plasma levels of amprenavir, was presented here today at the 40th annual meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

A total of 86 PI-experienced patients received Agenerase in combination with efavirenz or nevirapine with treatment based on phenotypic or genotypic resistance testing. Efavirenz and nevirapine are non-nucleoside reverse transcriptase inhibitors (NNRTIs) that have been shown to affect plasma levels of amprenavir.

"When low doses of ritonavir were added to the treatment regimen of PI-experienced patients taking efavirenz or nevirapine, preliminary data from this study showed that therapeutic plasma concentrations of amprenavir were maintained at 6 or 12 weeks," said G. Peytavin, X. Bichat-Cl. Bernard Hospital, Paris, France, principal author of the study.

Plasma concentrations (Cmin) of the treatment compounds were determined at two weeks after initiation of treatment and at week 6 or 12. When Cmin of amprenavir fell below therapeutic levels (100 ng/ml), patients physicians were offered a choice of two dosage regimens: Agenerase 600 mg twice a day plus 100 mg of ritonavir twice-a-day, or 1200 mg of Agenerase three times a day.

At week two, 70 percent (60/86) of patients -- 87 percent (52/60) of whom were in the group treated with efavirenz -- had Cmin of amprenavir below 100 ng/ml. Dosage adjustments of Agenerase were proposed for all 60 patients. The recommendations were carried out by the physician in 50 percent (30/60) of patients at week 6 or 12. Of patients that received a dose adjustment, 93 percent (28/30) received the Agenerase plus ritonavir combination. The Cmin of amprenavir rose above 100 ng/ml in all cases, despite the presence of efavirenz or nevirapine.
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Contact: Bob Szafranski
bszafranski@pcipr.com
312-558-1770
Public Communications Inc.
18-Sep-2000