Medication persistence among multiple sclerosis patients in Slovenia treated with dimethyl fumarate: a retrospective observational cohort study

Abstract Background Multiple sclerosis is a chronic, demyelinating inflammatory disease of the central nervous system. Medication persistence is an interval between initiation and last dose of a medication, followed by discontinuation of the applied medication. Aim The aim of this observational study was to evaluate Medication persistence and discontinuation reasons in Slovenian multiple sclerosis patients treated with dimethyl fumarate. Methods In this retrospective cohort study, we evaluated patients with relapsing-remitting multiple sclerosis treated with dimethyl fumarate as an initial monotherapy or switched from injectable disease modifying therapy medication during 2014 and 2021. Medication refills were extracted from Slovenian National Institute of Public Health Outpatient Medication Database. Medication persistence estimation was based on treatment gaps. Patients exceeding a 60-day gap were considered nonpersistent. Mean discontinuation time was assessed using survival analyses. Considering discontinuation reasons, patients were further divided into safety and inefficacy group. The impact of confounders was evaluated by Cox regression. Results A total of 259 patients were included (176 women, mean age 37 years). During the 7-year follow-up period, 118 patients discontinued treatment. The mean time to discontinuation was 5.6 years. A total of 85% and 77% of patients were persistent after 1 and 2 years of treatment, respectively. Age 30 and above was significantly related to higher medication persistence (P = 0.006). Conclusion The results of our study proved high medication persistence among our patients. The most frequent discontinuation reason was gastrointestinal adverse effects. Medication persistence requires interventions in younger patients with unstable disease course.