i found this post on page 639 on Naked Science Forum
lauracostis
23/01/2012
What they think happens in a migraine is that the vessels at the base of the head constrict, this causes the vessels higher up in the head to dilate as a compensatory mechanism to counteract for the decrease blood flow, this dilation causes the headache. The triptians selectively bind to 5ht receptors and cause the dilated vessels in the upper head to constrict, which relieves the headache. I get post-coital headaches and used to use sumatriptian, which worked great for the headaches and pois in general. The only problem was that the more I used sumatriptian the less effective it became, I also started to get more and worse headaches from over use(rebound headaches). Even if I did not get a postcoital headache, I would still take the sumatriptian and it would kick my pois in the ass pretty good. I would recommend using the Imitrex sparingly to treat only your worst postcoital headaches.