Pharmacokinetics of rifabutin during atazanavir/ritonavir co-administration in HIV-infected TB patients.

BACKGROUND & OBJECTIVE: Rifabutin (RBT) is the rifamycin that is recommended to treat tuberculosis (TB) in HIV-infected individuals during combination antiretroviral therapy (ART) containing HIV protease inhibitors (PIs). We studied the pharmacokinetics of rifabutin at doses of 300 mg thrice weekly and 150 mg daily during concomitant atazanavir/ritonavir (ATZ/r) administration in adult HIV-infected TB patients treated in the Revised National TB Control Programme (RNTCP) in India. METHODS: This was a multi-centric study conducted in 45 adult HIV-infected TB patients, who were being treated for TB with a RBT-containing regimen and an antiretroviral treatment regimen with ATZ/r, at doses of 300 mg thrice-weekly (n = 36) or 150 mg daily (n = 9). Serial blood draws at pre-dosing and at 1, 2, 4, 6, 8, 12 and 24 hours after drug administration were done. Plasma RBT was estimated by high pressure liquid chromatography (HPLC). RESULTS: The peak concentration (Cmax) of both doses were within the therapeutic range (0.45-0.90 µg/ml) of RBT. Proportion of patients having Cmax above or below the therapeutic range and trough concentration (Cmin) below the minimum inhibitory concentration of RBT did not significantly differ between the two doses. TB treatment outcomes were also similar at both doses. CONCLUSIONS: This is the first and only study from India reporting on the pharmacokinetics of RBT at 300 mg thrice weekly and 150 mg daily doses. Both doses yielded similar plasma RBT concentrations, outcomes and were well tolerated. RBT can be administered at either doses during ATZ/r co-administration in HIV-infected patients with TB.

Age, nutritional status and INH acetylator status affect pharmacokinetics of anti-tuberculosis drugs in children.

SETTING: The currently recommended dosages of rifampicin (RMP), isoniazid (INH), pyrazinamide (PZA) and ethambutol in children are extrapolated from adult pharmacokinetic studies, and have not been adequately evaluated in children. OBJECTIVE: To describe the pharmacokinetics of RMP, INH and PZA given thrice weekly in children with tuberculosis (TB), and to relate pharmacokinetics to treatment outcomes. METHODS: Eighty-four human immunodeficiency virus negative children with TB aged 1-12 years in Chennai and Madurai, India, were recruited. Phenotypic INH acetylator status was determined. Nutritional status was assessed using Z scores. During the intensive phase of anti-tuberculosis treatment, a complete pharmacokinetic study was performed after directly observed administration of drugs. At 2 and 6 months, drug levels were measured 2 h post-dose. Drug concentrations were measured using high performance liquid chromatography and pharmacokinetic variables were calculated. Multivariable regression analysis was performed to explore factors impacting drug levels and treatment outcomes. RESULTS AND CONCLUSIONS: Children aged <3 years had significantly lower RMP, INH and PZA concentrations than older children, and 90% of all children had sub-therapeutic RMP Cmax (<8 µg/ml). Age, nutritional status and INH acetylator status influenced drug levels. Peak RMP and INH concentrations were important determinants of treatment outcome. Recommendations for anti-tuberculosis treatment in children should take these factors into consideration.