Interrupted therapy: stopping and switching of the beta-interferons prescribed for MS.

A retrospective chart review of patients in British Columbia with multiple sclerosis prescribed beta-interferon (IFNbeta) between 1995 and 2001 was carried out to investigate reasons for the interruption of therapy. The highest proportion of interruptions (76/281; 27%) occurred in the first 6 months. The single most common reason was perceived lack of efficacy, cited by 84 of 281 (30%). Gender, disability, and disease duration were identified as factors influencing interruption of IFNbeta therapy.