An open study was performed on 20 women between 20 and 40 years of age in order to assess the effectiveness of a slow-release pharmacological formulation of dihydroergotamine in the prevention of menstrual migraine. Therapy was started two days prior to the expected date of menstruation and continued for five days after the onset of menstrual flow. Trial lasted for five months, four patients suspended the treatment: one because of side effects and three because of "ineffectiveness of drug". In the 16 patients who completed the study, there was a significant reduction both in intensity and duration of migraine compared to the month prior to treatment.