Sumatriptan, a selective 5-HT1B/1D receptor agonist, rapidly alleviates cluster headache symptoms by causing vasoconstriction of cranial blood vessels and inhibiting pro-inflammatory neuropeptide release. When administered via subcutaneous injection, it provides fast-acting relief by targeting serotonin receptors in the central and peripheral nervous system, effectively interrupting the pathophysiological cascade of cluster headache pain.