Course of therapy in patients with active relapsing-remitting multiple sclerosis despite first-line treatment.

First-line therapy in the studied population was based mainly on β-interferons and dimethyl fumarate. For most medications, the discontinuation of therapy or drug switching were very common and the main reason was total or partial treatment failure. These observations suggest the need for earlier implementation of more effective treatment, based on drugs with high efficacy, in the study population.