[Safety and effectiveness of interferon β-1a intramuscular therapy: results of the postmarketing drug surveillance in Japan].

To investigate the safety and effectiveness of the interferon β-1a intramuscular injection under clinical conditions in Japan, we conducted an all-case postmarketing surveillance with a 2-year follow-up of patients who were registered during the period between November 2006 (product launch) and December 2010. Case reports were collected from 397 institutions. The safety analysis included 1,476 patients, and the effectiveness analysis included 1,441 patients.