For a patient experiencing frequent migraines, which of the following medications is appropriate for prophylaxis?

Topiramate is an appropriate choice for prophylaxis in patients experiencing frequent migraines because it has been shown to reduce the frequency and severity of migraine attacks. As an anticonvulsant, it can stabilize neuronal excitability, which is thought to play a role in the pathophysiology of migraines. Clinical studies support its efficacy in lowering the incidence of migraine days per month and improving quality of life for individuals affected by this condition.

In contrast, the other medications listed are not typically used for migraine prevention. Sumatriptan is a triptan specifically designed for the acute treatment of migraines once an attack has begun, rather than for prevention. Ergotamine is also primarily utilized in the acute treatment of migraines and is not recommended for chronic use due to its side effects and risk of rebound headaches. Verapamil, while a calcium channel blocker that can be effective in certain headache disorders such as cluster headaches, is not first-line treatment for migraine prophylaxis and is less supported in the literature for this specific use.