The Clinical Pharmacokinetics of Rifampin and Ethambutol in HIV-Infected Persons with Tuberculosis

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Abstract
Background. The pharmacokinetics of rifampin and ethambutol in HIV-infected patients with tuberculosis (TB) are incompletely characterized. We examined the pharmacokinetics of rifampin and ethambutol in a cohort of patients with HIV-related TB who were treated in the United States. Methods. Serum drug concentrations were determined 2, 6, and 10 h after dosing in 36 HIV-infected patients with TB who were taking rifampin and in 49 who were taking ethambutol. Observed serum concentrations were compared with published normal ranges and published data. Results. With daily dosing of rifampin (600 mg), 26 (77%) of 34 patients (95% confidence interval [CI], 59%-89%]) had a low maximum concentration of rifampin (Conclusions. In HIV-infected patients with TB who are receiving rifampin and ethambutol, low maximum concentrations of rifampin and ethambutol were common. For patients with HIV-related TB, therapeutic monitoring of rifampin and ethambutol levels may help clinicians achieve target serum concentrations.