Which of the following is an effective medication for migraine prophylaxis?

Propranolol is effective for migraine prophylaxis because it is a beta-blocker that has been shown to reduce the frequency and severity of migraine attacks. It works by decreasing the excitability of the central nervous system and stabilizing vascular reactions that can contribute to migraines. Propranolol is particularly beneficial for individuals with frequent or debilitating migraines, and it is often one of the first-line treatments recommended in clinical practice for preventing migraine episodes.

Other options like ibuprofen and aspirin are nonsteroidal anti-inflammatory drugs (NSAIDs) primarily used for the acute treatment of migraine attacks rather than for prevention. Sumatriptan, a triptan medication, is also designed for acute treatment and works by constricting blood vessels and alleviating headache symptoms rather than preventing the occurrence of migraines. Hence, they do not offer the long-term prophylactic benefits that propranolol provides.