Ergotamine is an ergot alkaloid that acts as a potent vasoconstrictor and serotonin (5-HT1) receptor agonist, which helps to reduce cerebral blood vessel dilation and interrupt the neurovascular cascade associated with cluster headaches. It primarily works by binding to α-adrenergic and serotonin receptors, leading to vasoconstriction and interruption of inflammatory neurogenic processes that contribute to cluster headache pathophysiology.