 Twenty four RRMS patients over the age of 18, with similar degree of disability, and with an evolution of at last 6 months, who are in first-line immunomodulatory therapy and have a stable disease no more than one outbreak per year will be included in the present study. Patients will be administered a neuropsychological test battery selected for this study and divided into two sessions of one and a half-hour each. Emotional state will be assessed with the Beck Depression Inventory in a different session. Cognitive impairment is defined as the alteration of two or more neuropsychological tests. Patients will be divided randomly into two groups where one will receive placebo and the other one 4-AP for a period of four months in increasing doses. 