Drugs used in prophylaxis of a migraine are all except?

Prophylaxis of migraine is required if the attacks are frequent (>2-3 per month). The drugs useful for prophylaxis are: Propanolol is the most commonly used drug for prophylaxis of migraine attacks. Timolol, atenolol, metoprolol and nadolol can also be used but the drugs with ISA (e.g. pindolol) are ineffective. Calcium channel blockers like flunarizine (also blocks Na+ channels) is also effective Methysergide, cyproheptadine and TCAs like amitriptyline can also be used. Clonidine can be used orally for the prophylaxis of migraine attacks. Topiramate (anticonvulsant drug) has recently been approved for prophylaxis of migraine. Valproate and gabapentin also possess some prophylactic activity.