Multiple sclerosis (MS) is an inflammatory chronic demyelinating disease. Nowadays, there are several registered drugs aimed to control the disease activity. Because these drugs are given parenterally for years, it is of utmost importance to attain maximum adherence to treatment through close and permanent care of patients. The efficacy of the different registered drugs has been compared against placebo. Observational and head-to-head studies have shown controverted results in the degree of efficacy between the products. Despite the efficacy reported, a high proportion of patients will have a lack of response to treatment. Early identification of these patients is therefore essential in order to attempt other therapeutic approaches.