300 Section - When and why are people discontinuing multiple sclerosis disease modifying drugs: real world data from Saskatchewan and implications for rehabilitation services

Objectives : In multiple sclerosis (MS) care, early initiation of MS disease modifying drug treatment delays disability progression. Into older age, drug treatment may be associated with increased side effects without a continued benefit on disability progression. Rehabilitation interventions are important across the disease course and the main management approach after MS drug discontinuation. This study aimed to determine if age when MS drugs are discontinued is changing over time among people in the Saskatchewan MS Drugs Program. A secondary objective explored reasons for drug discontinuation.

Design: A chart audit was conducted for people living with MS who started an MS drug with the Saskatchewan MS Drugs Program between December 4, 1997, and April 30, 2025. Sex, age at drug start, the proportion who had discontinued drug and age at drug discontinuation were reported using descriptive statistics. Change in age of drug discontinuation over 28 years was explored using scatter plots with fitted linear regression. Primary reason for drug discontinuation was extracted and categorized.

Results: A total of 2644 people started an MS drug (70.7% female) prior to April 30, 2025. The mean age at drug start was 38.6 (±10.2) years. 1402 people (53.0%) had discontinued drug at a mean age of 48.2 (±12.4) years. Age at drug discontinuation decreased by 0.38 years for each additional year of data collection (p < 0.001). Of the patients who discontinued drug, 1316 (93.9%) included reasons for discontinuation categorized into the following groups: disease progression/activity (22.3%), non-adherence (15.4%), side effects (14.4%), moved out of province (10.6%), deceased (3.4%), family planning (2.6%), or other (31.3%).

Conclusion: Age at MS drug discontinuation has decreased by approximately a decade over the last 28 years. Disease progression is a common reason for drug discontinuation with important implications on the need for and timing of rehabilitation services.