A doseāfinding study to guide use of verapamil as an adjunctive therapy in tuberculosis
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jats:pInduction of mycobacterial efflux pumps is a cause of jats:italicMycobacterium tuberculosis</jats:italic> (Mtb) drug tolerance, a barrier to shortening antitubercular treatment. Verapamil inhibits Mtb efflux pumps that mediate tolerance to rifampin, a cornerstone of tuberculosis treatment. Verapamil's mycobacterial efflux pump inhibition also limits Mtb growth in macrophages in the absence of antibiotic treatment. These findings suggest that verapamil could be used as an adjunctive therapy for TB treatment shortening. However, verapamil is rapidly and substantially metabolized when coāadministered with rifampin. We determined in a doseāescalation clinical trial of persons with pulmonary tuberculosis that rifampināinduced clearance of verapamil can be countered without toxicity by the administration of larger than usual doses of verapamil. An oral dosage of 360 mg sustainedārelease (SR) verapamil given every 12 hours concomitantly with rifampin achieved median verapamil exposures of 903.1 ng.h/ml (AUC 0ā12h) in the 18 participants receiving this highest studied verapamil dose; these AUC findings are similar to those in persons receiving daily doses of 240 mg verapamil SR but not rifampin. Moreover, norverapamil:verapamil, R:S verapamil and R:S norverapamil AUC ratios were all significantly greater than those of historical controls receiving SR verapamil in the absence of rifampin. Thus, rifampin administration favors the lessācardioactive verapamil metabolites and enantiomers that retain similar Mtb efflux inhibitory activity to verapamil, increasing overall benefit. Finally, rifampin exposures were 50% greater after verapamil administration, which may also be advantageous. Our findings suggest that a higher dosage of verapamil can be safely used as adjunctive treatment in rifampinācontaining treatment regimens.</jats:p>
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Publication status: Published
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1532-6535
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National Institutes of Health (NIH) (2R01AI054504-20A1)