Measuring adherence and persistence to disease-modifying agents among patients with relapsing remitting multiple sclerosis

Objectives To measure disease-modifying agent adherence and persistence among patients with multiple sclerosis (MS). Design Retrospective cohort study. Setting Multispecialty, salaried group practice in southeast Michigan, between June 1, 2004, and June 30, 2006. Patients 224 insured adult patients with relapsing remitting MS with an outpatient visit. Main outcome measures Medical record–documented receipt of medication recommendation and prescription. Pharmacy claims data–derived measures of dispensing and among patients with two or more dispensings, medication possession ratios (MPRs), and proportion of gap days were estimated. Among those initiating agent use, persistence was estimated. Results Mean cohort age was 47.6 years, while 77% of participants were women and 39% were black. Of patients, 81.8% had a recommendation for a disease-modifying agent, 75.0% had a prescription, and 66.5% had two or more dispensings. Among those with two or more dispensings, mean MPR between the first and last dispensing date was 83.8% (95% CI 80.8–86.8), while mean MPR for the entire 24-month period was 68.0% (64.4–71.7). MPR for the 24-month period decreased with increasing drug copayments and was lower among black patients, while MPR between the first and last dispensing date increased with increasing age. Among those initiating therapy, 43% were nonpersistent with medications within 14 months. Conclusion Medication adherence and persistence among patients with relapsing remitting MS is far from monolithic. Measuring medication adherence and persistence among defined populations is useful for understanding the relationship between medication use and outcomes in practice and for targeting patients and programs to improve medication adherence.