1) Antimigraine drug 
<radiology> Treatment for migraine, can cause retroperitoneal fibrosis ... (12 Dec 1998) ... 
(meth″ĭ-sur´jīd) a potent serotonin antagonist and vasoconstrictor, used in the prophylaxis of migraine; also available as the maleate salt.
Methysergide is a vasoconstrictor drug used to prevent migraine and other recurring vascular headaches. It works by blocking the action of serotonin, a chemical that constricts blood vessels.