title: Effect of rifampicin-based antitubercular therapy on nevirapine plasma concentrations in South African adults with HIV-associated tuberculosis.
abstract: OBJECTIVE
  Nevirapine-containing antiretroviral therapy (ART) and rifampicin-based antitubercular therapy are commonly co-administered in Africa, where nevirapine is often the only available non-nucleoside reverse transcriptase inhibitor. Rifampicin induces the metabolism of nevirapine, but the extent of the reduction in nevirapine concentrations has varied widely in previous studies. We describe the steady-state pharmacokinetics of nevirapine during and after antitubercular therapy in South African patients.
  
  
  METHODS
  Sixteen patients receiving ART including standard doses of nevirapine were admitted twice for intensive pharmacokinetic sampling: during and after rifampicin-based antitubercular therapy.
  
  
  RESULTS
  Geometric mean ratios for nevirapine pharmacokinetic parameters during versus after antitubercular therapy were 0.61 [90% confidence interval (CI) 0.49-0.79] for Cmax, 0.64 (90% CI 0.52-0.80) for area under the curve up to 12 h (AUC(0-12)) and 0.68 (90% CI 0.53-0.86) for Cmin. Nevirapine Cmin was subtherapeutic (<3 mg/L) in six patients during antitubercular therapy (one of whom developed virological failure) and in none afterwards. There was no correlation between rifampicin concentrations and the degree of nevirapine induction assessed by the proportional change in nevirapine concentrations between the two admissions. The ratio of nevirapine AUC(0-12) to the AUC(0-12) of its 12-hydroxy metabolite was significantly lower in the presence of antitubercular therapy, consistent with induced metabolism.
  
  
  CONCLUSIONS
  Nevirapine concentrations were significantly decreased by concomitant rifampicin-based antitubercular therapy and a high proportion of patients had subtherapeutic plasma concentrations. Further study in African patients is required to determine the implications for treatment outcomes.
authors: Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, South Africa. karen.cohen@uct.ac.za
authors: Karen
authors: K
authors: Cohen
authors: Gilles
authors: G
authors: van Cutsem
authors: Andrew
authors: A
authors: Boulle
authors: Helen
authors: H
authors: McIlleron
authors: Eric
authors: E
authors: Goemaere
authors: Peter J
authors: PJ
authors: Smith
authors: Gary
authors: G
authors: Maartens
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000097:blood* / Q000627:therapeutic use; D004347:Drug Interactions / Q000502:physiology; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000097:blood* / Q000150:complications / Q000188:drug therapy; D015497:HIV-1; D006801:Humans; D008297:Male; D019829:Nevirapine / Q000097:blood* / Q000627:therapeutic use; D012293:Rifampin / Q000097:blood* / Q000627:therapeutic use; D013019:South Africa; D014376:Tuberculosis / Q000097:blood* / Q000150:complications / Q000188:drug therapy
chemical_list: D000995:Antitubercular Agents; D019829:Nevirapine; D012293:Rifampin