Migraine headaches affect 17 percent of women and 6 percent of men in the United States and fall into two classes: episodic migraines, defined as lasting less than 15 days per month, and chronic migraines that last at least 15 days per month for at least 3 months.
Even episodic migraines can cause serious lifestyle limitations, requiring preventive medication. All four drugs approved by the U.S. Food and Drug Administration for prevention of adult episodic migraine (the anti-epileptics, divalproex and topiramate, and the beta-blockers, timolol and propranolol) were found effective in a review of studies on the medications.
These drugs were better than placebo in reducing monthly migraine frequency by at least 50% in 200-400 patients per 1,000 treated, according to a the review of 215 randomized controlled trials and 76 nonrandomized studies. However, none of the approved drugs was significantly more beneficial than the others.
More details are in Shamiliyan et al. (2013). Preventive pharmacologic treatments for episodic migraine in adults. Journal of General Internal Medicine, 28(9), 1225-1237.