Background and Importance Several studies conclude that correct adherence of patients with multiple sclerosis (MS) is related to higher efficacy and lower risk of relapses, disease progression, hospitalisations, emergency department visits, and ultimately lower health care costs. Therefore, it is a priority to detect non-adherence in order to optimise therapy.

Aim and Objectives To assess adherence to daily oral treatment in people with MS. To perform a detailed descriptive analysis of non-adherent treatments, identifying reasons, previous treatments received and current status.

Material and Methods Using the Hospital’s outpatient module, a record was obtained of the corresponding dispensing dates between December 2017 and September 2023. This information was used to calculate adherence for treatments exceeding 6 months, which was complemented with the electronic medical record and patient interviews. A medication possesion rate (MPR) of less than 90% was considered non-adherence. Interruptions due to medical reasons were taken into account.

Results A total of 114 patients were included and 144 treatments were analysed, corresponding to 66 treatments with dimethyl fumarate (9 non-adherent, 13.6%), 63 with teriflunomide (3 non-adherent, 4.8%), 13 with fingolimod (2 non-adherent, 15.4%) and 2 treatments with ponesimod without adherence problems.

There was non-adherence in 14 treatments corresponding to 12 patients, with a median MPR of 84.4% (interquartile range 78.0 – 85.5%). Of these, 7 patients remained on the same treatment despite non-adherence, with no worsening of lesions detected by magnetic resonance imaging. 4 patients switched to another treatment and 1 patient discontinued treatment without switching to another treatment. Of the 12 patients, 7 had previously received other treatments, with glatiramer being the most common, along with interferon and teriflunomide.

Reasons for non-adherence in 14 treatments were adverse effects (4), missed doses (4) and in 6 patients we could not clearly identify the cause.

Conclusion and Relevance We found good adherence in almost all patients. In non-adherent patients the rate of medication possession remains high and did not translate in most cases into clinical worsening.

Adherence assessment and subsequent detection of non-adherent patients in MS is a key strategy for pharmaceutical interventions aimed at achieving better health outcomes and efficiency.

Conflict of Interest No conflict of interest.