Pharmacological enhancement of protease inhibitors with ritonavir: an update

Advances in HIV treatment since the approval of the first antiretroviral (ARV) medication have occurred at a rapid pace. However, resistance to these medications can occur quickly owing to inadequate plasma concentrations resulting from poor adherence related to intolerable drug toxicities and complex dosing schedules. Drug-drug and drug-food interactions can also result in inadequate ARV drug exposure. Ritonavir is a potent cytochrome P450 3A4 inhibitor and low doses can be used in combination with almost all protease inhibitors to overcome most drug-drug and drug-food interactions. Little toxicity can be attributed to the addition of low-dose ritonavir to an ARV regimen, and most patients find that the added pills do not adversely affect adherence. This article reviews the pharmacological use of ritonavir for pharmacokinetic enhancement (or boosting) and updates the clinical use of boosted protease inhibitors.