Efficacy of Various Durations of Isoniazid Preventive Therapy for Tuberculosis: Five Years of Follow-up in the IUAT Trial. International Union Against Tuberculosis Committee on Prophylaxis

A total of 28 000 persons with fibrotic pulmonary lesions compatible with tuberculosis were followed for five years after receiving 12, 24, or 52 weeks of preventive treatment with isoniazid or placebo.Compared with placebo, 12 weeks of isoniazid eliminated less than one-third, and 24 weeks eliminated two-thirds of the tuberculosis risk. Where preventive treatment is not currently practised, adopting a 24-week regimen could decrease the incidence of tuberculosis in such populations by 65%.Hepatitis, the only serious side-effect encountered, occurred infrequently but was more common among isoniazid recipients (0.5%) than among placebo recipients (0.1%).Fifty-two weeks of isoniazid prevented the most tuberculosis, but 24 weeks prevented more tuberculosis cases per case of hepatitis caused. Where preventive treatment is currently practised for 52 weeks, adopting a 24-week regimen would decrease hepatitis by one-third and increase tuberculosis by 40%.