Cytochrome P450 3A4 and P-glycoprotein (CYP3A4 & P-gp)

Cytochrome P450 3A4 (CYP3A4) is a major drug-metabolizing enzyme, and P-glycoprotein (P-gp) is an efflux transporter. Ritonavir inhibits both, increasing the bioavailability and half-life of co-administered drugs. This effect is exploited in HIV therapy to boost the levels of protease inhibitors and other antiretroviral agents. Ritonavir's inhibitory effect allows for lower and less frequent dosing of these drugs. At higher doses, ritonavir can also induce other CYP enzymes, leading to potentially complex drug interactions.

Other names

CYP3A4CYP3ACytochrome P450, family 3, subfamily A, polypeptide 4P-glycoproteinP-gpABCB1MDR1Multidrug resistance protein 1

Ritonavir inhibits CYP3A4 and P-glycoprotein, reducing the metabolism and efflux of co-administered drugs, leading to increased plasma concentrations and half-lives. While ritonavir primarily acts as an inhibitor it can also induce other CYP enzymes at higher doses, potentially decreasing the levels of some non-HIV medications.