Pharmacokinetics and pharmacodynamics of indinavir with or without low-dose ritonavir in HIV-infected Thai patients

Objectives: To describe the pharmacokinetics and pharmacodynamics of indinavir with or without low-dose ritonavir in human immunodeficiency virus (HIV)-infected Thai patients. Patients and methods: Thirty-six HIV-1 -infected patients who participated in HIV-NAT 005 study gave informed consent to record a pharmacokinetic curve 4 weeks after starting a regimen containing either indinavir 800 mg every 8 h (n = 19) or indinavir 800 mg + ritonavir 100 mg every 12 h (n= 17). Indinavir plasma concentrations were measured by HPLC. Pharmacokinetic parameters were calculated by non-compartmental methods. Results: The median (interquartile range; IQR) body weight of the 36 patients (11 females and 25 males) was 60 (54-72) kg. Median and IQR values for indinavir AUC, C-max and C-min were 20.9 (13.1-27.0) mg.h/L, 8.1 (6.6-9.4) mg/L and 0.13 (0.09-0.27) mg/L, respectively, for indinavir 800 mg every 8 h, and 49.2 (42.5-60.4) mg.h/L, 10.6 (8.5-13.2) mg/L and 0.68 (0.43-0.77) mg/L, respectively, for indinavir 800 mg + ritonavir 100 mg every 12 h. These values are not largely different from values found in Caucasian patients, with the exception of relatively high peak levels of indinavir in Thai subjects. Cut-off values for optimal virological efficacy were an indinavir Cmin of 0.10 and 0.25 mg/L for the every 8 h and the every 12 h regimen, respectively; patients with an indinavir AUC greater than 30 (every 8 h regimen) or 60 (every 12 h regimen) mg.h/L were at increased risk of developing nephrotoxicity. Conclusions: Indinavir pharmacokinetics and pharmacodynamics in Thai HIV-1-infected patients are similar to those described in Caucasian patients, despite an overall lower body weight in this population.