[Interferon-beta 1a in relapsing-remitting multiple sclerosis. First report of a Mexican population].

OBJECTIVE: We present the results of a prospective and a longitudinal study of IFN-beta 1a (Rebif) in the treatment of Mexican patients with relapsing-remittin multiple sclerosis (MS). PATIENTS AND METHODS: Twenty five patients were included, all of them fulfilled the diagnostic criteria proposed by Poser, had a clinical evolution of at least 2 years, had 2 to 3 acute attacks of MS in the 12 months preceding study entry and an EDSS < 5.5. Six patients were excluded from the trial, one because of anaphylactic shock, 2 progressed to the chronic form and 3 decided not to continue in the study. These patients were considered as treatment failures and represented 24% of the participants entering the trial. The remaining 19 patients (mean age 29.8, 74% females) completed 2-year follow-up. The mean time of disease duration was 48.8 months. Six million units of IFN-beta 1a were applied thrice weekly, in 8 patients (42%) dosage reduction to 6 millions units twice a week was necessary because of leukopenia or elevation in liver enzymes. RESULTS: In the year before treatment with IFN-beta 1a patients had 2.7 +/- 0.93 acute attacks, after treatment the mean number of acute attacks per year was reduced to 1.94 +/- 2.39 (28.9% reduction). When analyzed by gender there was a 62.9% reduction in acute episodes per year in women and a 27.7% reduction in men (p < 0.05). The most frequent side effects were fatigue, headache, local skin reactions, depressed mood, myalgia, weight variations and somnolence. A few patients developed leukopenia, anemia or elevated liver enzymes. In 31.25% of the patients there was an increase in the number of lesions on MRI, in 31.25% there was a reduction in the number of lesions and in 37.5% no change was noted. CONCLUSION: The best-tolerated dose of IFN-beta 1a was 12 million units/week in women and 18 million units/week in men.