Managing Drug Interactions in the Treatment of HIV-Related Tuberculosis

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The Role of Rifamycins in Tuberculosis Treatment

Despite the complexity of these drug interactions, the key role of the rifamycins in the success of tuberculosis treatment mandates that the drug-drug interactions between the rifamycins and antiretroviral drugs be managed, not avoided by using tuberculosis treatment regimens that do not include a rifamycin or by withholding antiretroviral therapy until completion of anti-tuberculosis therapy among patients with advanced immunodeficiency. In randomized trials, regimens without rifampin or in which rifampin was only used for the first two months of therapy resulted in higher rates of tuberculosis treatment failure and relapse ^{5, 6}. The sub-optimal performance of the regimen of two months of rifampin (with isoniazid, pyrazinamide, and ethambutol) followed by 6 months of isoniazid + ethambutol was particularly notable among participants with HIV co-infection ⁵. Therefore, patients with HIV-related tuberculosis should be treated with a regimen including a rifamycin for the full course of tuberculosis treatment, unless the isolate is resistant to the rifamycins or the patient has a severe side effect that is clearly due to the rifamycins.

Furthermore, patients with advanced HIV disease (CD4 cell count < 100 cells/mm³) have an increased risk of acquired rifamycin resistance if treated with a rifamycin-containing regimen administered once or twice-weekly ^{1, 7}. The rifamycin-based regimen should be administered daily (5-7 days per week) for at least the first 2 months of treatment among patients with advanced HIV disease ^{8, 9}.