Low‐dose indinavir in combination with low‐dose ritonavir: steady‐state pharmacokinetics and long‐term clinical outcome follow‐up

Objectives To evaluate the long‐term efficacy and pharmacokinetics of indinavir (IDV)/ritonavir (RTV) 400/100 mg twice a day in combination with two nucleoside reverse transcriptase inhibitors. Methods The study was retrospective with a prospective pharmacokinetic study at a single centre. All HIV‐1‐infected patients who started the regimen in the period from January 1999 to February 2001 were included in the study. Plasma HIV RNA and CD4 cell counts were recorded from baseline to week 120. Results were evaluated as intention‐to‐treat and on‐treatment analyses with separate analyses for protease inhibitor naive and experienced patients. Patients who were still on the regimen by August 2001 were asked to participate in a pharmacokinetic evaluation. Results Twenty‐one patients started treatment with the regimen (median follow‐up: 116 weeks). The percentage of patients with below 20 HIV‐1 RNA copies/mL was 70.0% at week 120 and the median CD4 cell count increased from 320 to 607 cells/μL (P=0.062). The median IDV morning and evening Cmin were 434 ng/mL and 220 ng/mL, respectively. Conclusions Treatment with the IDV/RTV 400/100 mg regimen appears to be efficacious for up to 2 years. However, rather low IDV Cmin suggests that the regimen should be evaluated further before its widespread use and that the regimen probably should be guided by pharmacokinetic evaluation.