The potential for hepatotoxicity is a well-recognized feature of therapy with a number of DMARDs in rheumatoid arthritis (RA), with methotrexate (MTX) being the most common utilized. Concomitant use of other hepatotoxic agents has the potential to compound the risk of significant liver damage. Among these, isoniazid (INH) is increasingly used in RA patients receiving MTX with evidence of latent tuberculosis infection (LTBI) or prior active tuberculosis for whom TNF inhibitor therapy is planned.