Metabolism hiv protease inhibitors

Most protease inhibitors have poor oral bioavailability. High-fat meals substantially increase the bioavailability of some, such as nelfinavir and saquinavir, whereas the bioavailability of indinavir is decreased, and others are essentially unaffected. All are substrates for the CYP3A4 isozyme of CYP450, and individual protease inhibitors are also metabolized by other P450 isozymes. Metabolism is extensive, and very little of the protease inhibitors are excreted unchanged in urine. Dosage adjustments are unnecessary in renal impairment. Distribution into some tissues may be affected because protease inhibitors are substrates for the P-glycoprotein multidrug efflux pump. The presence of this pump in endothelial cells of capillaries in the brain may limit protease inhibitor access to the CNS. The HIV protease inhibitors are all substantially bound to plasma proteins, specifically α1-acid glycoprotein. This may be clinically important, because the concentration of α1-acid glycoprotein increases in response to trauma and surgery.