Experience of a combination including indinavir 400 mg plus ritonavir 200 mg twice daily in HIV-infected patients: pharmacokinetic data.

Low doses of ritonavir, a strong inhibitor of cytochrome P450 3A4, enhances the pharmacokinetic profile of indinavir with increased serum levels. We assessed the indinavir-ritonavir 400/200 twice daily combination in 17 HIV-infected patients focusing on the pharmacokinetic data and the tolerance of this regimen. IDV trough and peak concentrations were measured by high-performance liquid chromatography. Median indinavir trough and peak concentrations were 553 ng/ml and 3626 ng/ml, respectively. A good tolerance was observed except for three patients who experienced a major toxicity. Only one dose adjustment was related to indinavir toxicity. Considering the fact that Cmax is mainly responsible of the adverse effects, particularly renal stones, the indinavir-ritonavir 400/200 mg twice daily regimen offers a well-tolerated combination with an increased Cmin but a lower Cmax compared with both the standard tid regimen and higher dose of IDV-RTV regimens.