(HealthDay News) — In individuals at high-risk for tuberculosis, three months of combination therapy with rifapentine plus isoniazid is as effective as nine months of isoniazid alone, and has significantly higher treatment completion rates, according to a study published in the Dec. 8 issue of the New England Journal of Medicine.

Timothy R. Sterling, M.D., from the Vanderbilt University School of Medicine in Nashville, Tenn., and colleagues compared three months of directly observed once-weekly rifapentine (900mg) plus isoniazid (900mg) combination therapy, with nine months of self-administered daily isoniazid therapy (300mg), in 7,731 individuals at high risk for tuberculosis. A total of 3,896 individuals from Brazil, Canada, Spain, and the United States were randomly allocated to receive combination-therapy, and 3,745 individuals to receive only isoniazid. Participants were followed up for 33 months. Confirmation of tuberculosis was the primary end point of the study, with a non-inferiority margin of 0.75%.

The investigators found that seven and 15 patients developed tuberculosis in the combination-therapy and isoniazid-only groups, respectively (cumulative rate, 0.19 and 0.43%, respectively), with a difference of 0.24%. The rates of treatment completion were significantly higher in the combination therapy versus the isoniazid-only groups (82.1 and 69%, respectively). The rates of permanent drug discontinuation due to an adverse event were 4.9 and 3.7% in the combination-therapy and isoniazid-only groups, respectively. The rates of investigator-assessed drug-related hepatotoxicity were 0.4% in the combination-therapy group and 2.7% in the isoniazid-only group.

“A three-month course of once weekly rifapentine plus isoniazid represents an advance in our ability to treat persons with latent Mycobacterium tuberculosis infection,” the authors write.

Several of the study authors disclosed financial ties to the pharmaceutical industry.

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