Drug-use patterns and severe adverse events with disease-modifying drugs in patients with multiple sclerosis: a cohort study based on German claims data

Purpose: To describe drug-use patterns in patients with multiple sclerosis (MS) using disease-modifying drugs (DMDs) and to estimate the incidence of severe adverse events (SAEs) of treatment. Methods: We conducted a cohort study within the German Pharmacoepidemiological Research Database between January 1, 2006 and December 31, 2013. MS patients on DMDs were described in terms of clinical characteristics and drug-use patterns. Next, we assessed the incidence of AEs in new users of fingolimod, natalizumab, glatiramer acetate, and IFNβ(1a). Results: Among approximately 11 million insured members of German Statutory Health Insurance, the DMD-user cohort comprised 15,377 patients with MS, with a mean age of 39.6 years and 68% females. Nearly half of all DMD users had a diagnosis of depression, with prevalence ranging from 40.1% for IFNβ(1a) to 62.3% for immunoglobulins. The overall rate of MS relapses per patient and year was 0.34 (95% CI 0.33–0.34). During an average follow-up of 1,650 days, the majority (42.4%) of MS patients were adherent to DMD treatment (“continuous single users”), followed by patients interrupting treatment (39.5%, “interrupters”). Switch of DMD treatment (11.9%) was less frequent, and only 5.6% discontinued treatment. Treatment discontinuation was most common in users of natalizumab (7.5%) and IFNβ(1b) (7.0%). The most frequent SAE was hospitalization for depression, followed by any infectious disease and any malignancy. The incidence rate of all adverse events did not significantly differ across different DMDs. Conclusion: Treatment discontinuation with DMDs and treatment switch were rare. Causes of rather frequent DMD-treatment interruption have to be evaluated in further studies based on primary data collection. Active safety monitoring of new DMDs based on claims data requires large data sets to detect rare AEs and availability of up-to-date data.