Pozen's migraine drug answers pained call for new tablet.

There may be some doubt about what's just "a bad headache" and what's a migraine, but those who suffer the latter are absolutely sure what they're feeling. Often, their initial clue is the dreaded "prodrome," a sense that the migraine is about to occur. Then begin the throbbing, pulsing pain and extreme sensitivity to light and sound, maybe with nausea and changes in vision, such as the appearance of auras.

The symptoms are distinct. But sufferers don't want to debate whether all these mean a genuine migraine. They just want the dizzying pain to go away.

Migraine headaches are less common than tension-type headaches, says the American Council for Headache Education, but they still afflict 25 million to 30 million people in the U.S., about 6 percent of all men and 18 percent of all women, or about 12 percent of the whole population.

Two-thirds or more of migraine victims are women (there's believed to be a hormonal link), and about half of the unlucky will first experience their migraines in childhood or adolescence.

The cause is unknown. Most likely, the migraine pain comes from blood vessels and nerves around the brain that swell as a result of activity in the brain…