Antiepileptics
Divalproex sodium and its analog sodium valproate were established as effective in migraine prevention in multiple class I studies.25 There is consistent evidence from 5 studies that divalproex sodium and the related compound, sodium valproate are both effective in decreasing headache frequency.26 The most common side effects seen with divalproex sodium were gastrointestinal (GI) symptoms, including nausea and vomiting. More serious adverse effects include thrombocytopenia, hepatitis, and pancreatitis. Valproate is class D in terms of pregnancy risk, and should be avoided in women of child bearing age. The other widely used antiepileptics is topiramate, which is thought to be as effective as propranolol.25 Topiramate was tested at doses of 50-100 mg and was found to have a 50% reduction in monthly migraine frequency.23 Some of the common side effects of topiramate include paresthesias, fatigue, cognitive side effects, and anorexia, which can lead to at times unfavorable weight loss. Rare but more serious side effects are the development of kidney stones and angle-closure glaucoma. It is usually started at doses of 15-25 mg daily, and slowly increased until efficacy or side effects are reached.20
The use of other anticonvulsants for the treatment of migraine has been less well supported. Gabapentin was found to be ineffective in 1 trial while another randomized control trial demonstrated that doses of 1800-2400 mg were effective in reducing the frequency of attacks.27 Carbamazepine at doses of 600-1200 mg/day may be effective, according to the few trials that have been conducted.28 The most common side effects with gabapentin and carbamazepine were dizziness and drowsiness.13 Lamotrigine and clonazepam are medications that have not been thoroughly evaluated, but are used in clinical practice.29