Sumatriptan, a selective 5-HT1B/1D receptor agonist, acts by causing vasoconstriction of cranial blood vessels and inhibiting neuropeptide release in the trigeminovascular system. When used for cluster headache, it rapidly alleviates pain by reducing inflammatory neurogenic processes and interrupting the trigeminal nerve's pain signaling cascade. The medication provides quick symptomatic relief by targeting the underlying pathophysiological mechanisms of cluster headache episodes.