Managing Drug Interactions in the Treatment of HIV-Related Tuberculosis
Treatment of latent TB infection (LTBI) is increasingly advocated in persons with HIV co-infection. Recommended options include daily self-administered isoniazid 300 mg for 9 months (9H) or daily self-administered rifampin 600 mg for 4 months (4R).93 Isoniazid is the clear preference for treating LTBI in a patient on drugs that have unfavorable interactions with rifamycins. No adjustment of ART dosing is required with the 9H regimen. Use of 4R would require the same dose adjustments as noted above for rifampin-based therapy of active TB disease. There are no data published on the use of rifabutin for LTBI. The Guideline Development Group suggests that rifabutin should be used for LTBI only if there is a compelling need for short-course treatment of LTBI, and/or if neither 9H nor 4R can be used. Recently a new regimen of 12 once-weekly doses of isoniazid 900 mg plus rifapentine 900 mg administered as directly observed therapy (DOT) has been recommended for use in persons who are HIV-uninfected or in persons with HIV who are otherwise healthy and not receiving ART.94 There are no data yet regarding the magnitude of induction of metabolizing enzymes that would be expected with once-weekly rifapentine at the recommended dose for LTBI; a manufacturer-sponsored study evaluating the effects of once-weekly and daily rifapentine on efavirenz is underway.