Absence of transaminase elevation during concomitant methotrexate and isoniazid therapy

To the Editor: It has become the standard of care to screen patients for latent tuberculosis infection (LTBI) prior to initiating tumor necrosis factor-α (TNF-α) antagonists, and treat with isoniazid (INH). Unfortunately, INH has been associated with hepatotoxicity. Estimates suggest that transaminase elevations may be seen in as many as 0.1% to 10% of patients treated with INH1,2. Patients with rheumatic disease may already be receiving potentially hepatotoxic medications such as methotrexate (MTX). Although the doses of MTX typically employed to treat rheumatic diseases are generally considered to be safe, mild reversible hepatotoxicity is common, and isolated cases of irreversible liver damage have been described3,4. The combination of 2 potentially hepatotoxic medications raises significant concern regarding safety. We describe the results of concomitant treatment with MTX and INH on hepatic function in a retrospective case series. … Address correspondence to Dr. A.M. Manadan, Rush University Medical Center, 1725 W. Harrison St., Suite 1017, Chicago, IL 60612. E-mail: amanadan{at}rush.edu