Abstract
Background. Because of side effects, adherence to the treatment with β interferons in multiple sclerosis (MS) is low, leading to decreased treatment efficacy. This can be challenging, especially in healthcare systems where these medications are the only therapeutic option for the treatment of MS. Materials and Methods. The number of missed doses was calculated as a difference between the number of doses a patient had to withdraw from the treatment start to the cut-off date and the real number of doses taken from the MS unit. Missed doses were compared to gender, age, time since the diagnosis, time from the diagnosis to the treatment start, clinical type of MS, expanded disability status scale (EDSS), and duration of the treatment. Results. The adherence rate during the follow-up period was 73.8%. Patients above 40 years of age (P<0.005), higher EDSS (P<0.001), longer duration of the disease (P<0.001), longer waiting time from the diagnosis to the treatment initiation (P<0.001), and longer time on interferons (P<0.001) had lower adherence rates to the treatment. Conclusions. The findings were in correlation with studies that have used similar criteria for the determination of adherence and supported reports that adherence rate decreases with time and poses a challenge to the overall efficacy of the treatment.