Background and importance Adherence to treatment is a key factor in the control of symptoms of multiple sclerosis and the risk of relapses with adherence exceeding 80–85% is lower. Oral treatments can improve adherence.

Aim and objectives To evaluate adherence to oral disease modifying therapies (oral-DMT) in multiple sclerosis and to determine factors that can influence this adherence.

Material and methods This was a retrospective study of adherence to oral-DMT for multiple sclerosis, from 10 February 2017 to 10 March 2019, in a general university hospital with a reference population of 361 526 inhabitants. All patients who had been dispensed oral-DMT in the indicated period (with at least 6 months of treatment) were selected. Dates and amount dispensed to calculate the percentage of adherence and persistence of treatment, as well as demographic (sex, age) and therapeutic (previous treatments, treatment stopped, subsequent treatments) data were recorded. The data were analysed statistically with the SPSS programme V.24.

Results Eighty-seven patients, 56 (64.4%) women, with a mean age of 46 years (SD 13.3) were included: 45 (51.7%) were treated with fingolimod, 22 (25.3%) with teriflunomide and 20 (23%) with dimethylfumarate. The majority (68, 78.2%) had been treated previously with injectable DMT, 36 (52.9%) with one drug, 15 (22.1%) with two drugs and 17 (25.1%) with ≥3 drugs. Fifteen (17.2%) patients finished treatment during the study period. The mean adherence rate was 94.6% (SD 16.4): for fingolimod it was 93.2% (SD 18.9), for teriflunomide 99.2% (SD 11.4) and for dimethylfumarate 92.7% (SD 14.4). Five patients treated with fingolimod, three treated with dimethylfumarate and two treated with teriflunomide had adherence <80%, with no significant differences between the drugs. Mean persistence of treatment was 6.7 years (95% CI 6 to 7.3). We did not find statistically significant differences in adherence (in percentages or by classifying it as <80% or ≥80%) based on whether patients had been previously treated or based on the number of previous treatments. There was no correlation between percentage adherence and duration of treatment.

Conclusion and relevance We observed high adherence to oral-DMT with a mean rate of 94.6%. Only 10 (11.5%) patients had adherence <80%. This value is higher than those observed with injectable DMT (41–88%) and similar to the values obtained with oral drugs. Moreover, persistence of treatment was long.

References and/or acknowledgements No conflict of interest.