The calcium antagonist properties of cyproheptadine: implications for antimigraine action.

Cyproheptadine is equipotent (IC50 = 41 to 45 nM) in blocking contractions of canine basilar artery segments induced by serotonin, norepinephrine, potassium, or calcium. Methysergide and amitriptyline display variable potencies in inhibiting contractions depending on the initiating agent. Propranolol, at concentrations to 10 micromolar, had minimal effect on vessel contractions. We conclude that the primary action of cyproheptadine in preventing induced contractions of the canine basilar artery is antagonism of calcium channels. This action is unique among drugs used for migraine prophylaxis and may have important implications for the treatment of headache and other neurologic disorders.