<qa>  What is the name of the medication that is used for migraine prevention?- Patients using one or more of the following medications before study entry: more than 1 type of migraine prevention medicine in the past 6 weeks, tramadol within 30 days, vitaminsherbal remedies or non-drug-related remedies for migraine for 30 days, St. Johns Wort within 30 days, investigational drug in past 30 days or any other disallowed medications 