Which of the following drug is not used for prophylaxis of migraine?

Propranolol 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. Diltiazem, verapamil and nimodipine can also be used. Methysergide, cyproheptadine and TCAs like amitriptyline, imipramine and noriptyline 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.