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. Of the patients included in the safety analysis, 86.3% had relapsing-remitting multiple sclerosis. The most common adverse drug reaction was pyrexia (19.24%). Serious adverse events included multiple sclerosis relapse (26 cases) and abnormal hepatic function (10 cases). In the effectiveness analysis, the annualized relapse rate improved significantly from 1.07 to 0.29 (P < 0.001). There was also a significant improvement in in the expanded disability status scale from 3.08 to 2.94 (P < 0.001). The results of the safety and effectiveness profile were consistent with those in previous reports.