SIDE-EFFECT PROFILE OF INTERFERON BETA-1B IN MS - RESULTS OF AN OPEN-LABEL TRIAL

To determine which patients are prone to side effects from interferon beta-1b and which side effects are most troublesome, we studied 72 pat ients with clinically definite MS who were started on interferon beta- 1b after its release and found that the side effects significantly ass ociated with treatment included skin reactions, flu-like symptoms, fat igue, leukopenia, new or worsened depression, and new or worsened head ache. Of these, only fatigue and depression were significantly associa ted with discontinuance of therapy. Moreover, the course of disease be fore initiation of treatment also had a significant impact on the like lihood of discontinuing medication. Thus, despite an apparently simila r therapeutic benefit (as judged by the similarly reduced attack rate in each group), patients with a secondary chronic progressive course w ere more likely to discontinue treatment (63%) than patients with eith er a relapsing/progressive course (18%) or a remitting/relapsing cours e (7%). Indeed, in the final regression equation, the only factors sig nificantly related (r = 0.875) to the discontinuance of therapy were f atigue (p < 0.0001), a fatigue-depression interaction (p < 0.0001), an d a chronic progressive course of disease (p < 0.0001). Thus, if futur e clinical trials are to provide useful information on the value of in terferon beta-1b in progressive MS, the side effects of fatigue and de pression will need to be ameliorated to limit the drop-out rate from s uch trials.