Lisinopril is an angiotensin-converting enzyme (ACE) inhibitor that, while not a primary treatment for cluster headache, has been studied for potential off-label use in prophylactic management. Its mechanism involves blocking the conversion of angiotensin I to angiotensin II, which may reduce vascular inflammation and potentially modulate neurovascular pain pathways associated with cluster headaches. However, its efficacy in cluster headache treatment remains limited and not conclusively established.