Methysergide (MSG)

Methysergide is a prescription drug formerly used for prophylaxis of cluster headaches/migraine headaches, but is no longer recommended due to retroperitoneal/retropulmonary fibrosis. Methysergide is used to treat headaches such as migraine and other recurrent throbbing headaches. Methysergide is one of the most effective medications for the prevention of migraine, but not for the treatment of an acute attack. It is also used in carcinoid syndrome to treat severe diarrhea. It may also be used in the treatment of serotonin syndrome. Methysergide interacts with serotonin (5-HT) receptors. Its therapeutic effect in migraine prophylaxis has been associated with its antagonism at the 5-HT2B receptor. Furthermore, it is an antagonist at the 5-HT2C receptor, while at the 5-HT1A receptor it serves as a partial agonist. It is known to have partial agonisteffects on some of the other 5-HT receptors as well.