Clopidogrel, which is also known as Plavix, is a drug used to prevent strokes and heart attacks.  It works by preventing platelets from sticking together and causing a blood clot which can block a vessel in the heart or brain.  Platelets also tend to become sticky in patients during a migraine attack, which is how this drug might help migraine sufferers.  A British physician reported that a small number of patients given this drug stopped having migraine headaches after many years of unsuccessful treatments.  A large study is currently under way to prove that this drug in fact works better than a placebo.