Background and Importance Multiple sclerosis (MS) population has been aging in parallel to the increasing life expectancy of the general population. This could be related to potentially inappropriate medication prescriptions, drug-drug interactions and therapeutic non-adherence.

Aim and Objectives Determine the prevalence of polymedication in an MS population aged 55 years or more and provide therapeutic recommendations to adjust treatment of the patient.

Material and Methods Observational, cross-sectional, study that included patients over 55 years of age with MS at a tertiary level hospital between December 2022-February 2023. Demographic variables: age, sex, date of MS diagnosis, type of MS and the Expanded Disability Status Scale (EDSS). Medication, polypharmacy (five or more drugs), major polypharmacy (10 or more drugs), anticholinergic burden, potentially inappropriate medication, drug-drug interactions (Lexicomp® database) and non-adherence to concomitant medication were collected. Statistical analysis was carried out with R Commander® software. Data was obtained from electronic prescription (Prisma®) and medical records (Diraya®) applications.

Results 95 MS patients aged 55 years or older were included. 68.4% were women. The median age was 61 years (IQR 58–65). Median age at the diagnosis 45.2 years (IQR 38.5–50.2). Type MS: recurrent remitting (71.6%), secondary progressive (19%) and primary progressive (9.4%). Median EDSS scale 2 (IQR 1–3). The most frequent disease-modulating drugs (MSD) were: interferon (23.1%), fampridine (16.8%), teriflunomide (14.7%), fingolimod (8.4%) and glatiramer acetate (7.4%). Median number of drugs concomitant with MSD 6 (IQR 3–9). Polypharmacy 68.4%. High treatment complexity index 40%. Non-adherence to concomitant medication was identified in 84.4% of patients and drug-drug interactions in 56.2% (category D 83.8% and X 16.2%). Anticholinergic load: no risk 20%, moderate risk 22.1% and high risk 57.9%. A total of 20 pharmaceutical interventions were carried out in 17 patients (17.9%), the potentially inappropriate medication criterion was responsible for 11 interventions, non-adherence for seven and interactions for two. Of the 11 interventions on inappropriate medication criteria, nine (81.8%) were accepted, resulting in the discontinuation of 15 drugs that were appropriately prescribed.

Conclusion and Relevance Polypharmacy plays a very important role in adult MS patients as it is associated with a higher prevalence of inappropriate medication prescriptions, drug-drug interactions and therapeutic non-adherence.

Conflict of Interest No conflict of interest.