Isoniazid preventive therapy, hepatitis C virus infection, and hepatotoxicity among injection drug users infected with Mycobacterium tuberculosis.

Treatment of latent Mycobacterium tuberculosis infection with isoniazid can cause hepatotoxicity, but the risk of isoniazid-associated hepatotoxicity among persons coinfected with hepatitis C virus (HCV) is unknown. We conducted a prospective study among 146 injection drug users with M. tuberculosis infection and normal baseline hepatic transaminase values who were treated with isoniazid. Of 146 participants, 138 (95%) were HCV-seropositive. Thirty-seven participants (25%) were human immunodeficiency virus (HIV)-seropositive. Thirty-two (22%; 95% confidence interval [CI], 16%-30%) of 146 participants developed transaminase value elevations to >3 times the upper limit of normal. Transaminase value elevation was associated with concurrent alcohol use but not with race, age, presence of hepatitis B surface antigen, HIV-1 infection, or current injection drug use. Isoniazid was withdrawn from 11 participants (8%; 95% CI, 4%-13%). Of 8 deaths during follow-up, none were attributed to isoniazid-associated hepatotoxicity. The risk of transaminase value elevation and drug discontinuation for HCV-infected persons receiving isoniazid was within the range reported for populations with lower HCV prevalence.