Nevirapine plasma concentrations and concomitant use of rifampin in patients coinfected with HIV-1 and tuberculosis

OBJECTIVES: In countries with high numbers of HIV/tuberculosis coinfection nevirapine and rifampin are used extensively. However, limited data are available about whether or not nevirapine and rifampin can be safely coadministered without the plasma concentration of nevirapine falling below therapeutic levels. METHODS: Blood samples for determination of nevirapine plasma concentrations were collected from patients using nevirapine 200 mg twice daily with or without concomitant rifampin. Bivariate and multivariate linear regression models were used to investigate factors possibly related to nevirapine concentrations. RESULTS: We received 74 blood samples from patients using nevirapine plus rifampin, and collected blood samples from an equal number of controls using nevirapine only. Groups were similar for age, gender, weight, height and body mass index (BMI). In the rifampin group the mean nevirapine concentration was 5.47 +/- 2.66 mg/l, whereas in the control group the mean nevirapine concentration was 8.72 +/- 3.98 mg/l. In the rifampin group seven nevirapine trough concentrations were low (< 3.1 mg/l), while in the control group two patients had low nevirapine trough concentrations (P = 0.164). In the multivariate linear regression analysis, corrected for time after drug intake, the use of rifampin was significantly (P < 0.001) associated with lower nevirapine plasma concentrations, whereas higher BMI reached borderline significance (P = 0.065). CONCLUSION: Although nevirapine plasma concentrations were 3.3 mg/l lower when co-administered with rifampin, still more than 86% of these patients had nevirapine plasma concentrations > 3.1 mg/l. Our results suggest that from a pharmacological point of view the majority of Thai coinfected patients, who have low BMIs, reach nevirapine plasma concentrations that are adequate for treatment of HIV. However this can only be undertaken if nevirapine plasma concentration monitoring is available and can be closely followed.     

Interruptions of tenofovir/emtricitabine-based antiretroviral therapy in patients with HIV/hepatitis B virus co-infection

Thai patients enrolled in STACCATO with HIV/hepatitis B virus (HBV) co-infection and tenofovir/emtricitabine-based antiretroviral therapy (ART) were randomly assigned to continuous treatment or CD4 cell count-guided interruptions. HBV replication was suppressed below detection in 15/16 patients. Structured treatment interruption increased transaminases and HBV viraemia in five of six patients; one flare was severe. Conversion to anti-hepatitis Be occurred with continuous treatment only. Tenofovir/emtricitabine-containing ART is highly effective in controlling chronic HIV/HBV co-infection but treatment should not be interrupted.     

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, Cmax and Cmin were 20.9 (13.1-27.0) mg x 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 x 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 x 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