Azathioprine in multiple sclerosis: the cons.

Azathioprine has the longest continuing history of clinical use in the treatment of multiple sclerosis (MS) of any immunosuppressive therapy besides corticosteroids. To date, 19 clinical trials of azathioprine in MS have been reported, and another eight are under way. A review of the reported trials indicates little evidence for a therapeutic effect in MS. This and the lack of evidence for a specific immune alteration in the pathogenesis of MS are relative contraindications for the use of high risk immunosuppressive therapies in this disease. A further caveat is raised by a recent report suggesting that azathioprine may have contributed to an increased incidence of carcinomas in MS patients treated with this drug. In view of these considerations, perhaps the best position to take at the present time is to encourage investigators already engaged in controlled clinical trials of azathioprine to complete their work, so that this data can be considered before new studies of azathioprine in MS are undertaken.