Antiepileptic drugs: indications other than epilepsy

Antiepileptic drugs (AEDs) are increasingly used for the treatment of several non-epileptic neurological conditions and psychiatric disorders. Most of the information available on the use of these agents in clinical disorders outside epilepsy is from case series, uncontrolled studies or small randomised clinical trials, and their apparent efficacy requires confirmation through well designed, large, phase III trials. With regard to neurological conditions other than epilepsy, experimental evidence for the efficacy of AEDs is only available for the treatment of patients with trigeminal neuralgia, neuropathic pain syndromes, migraine and essential tremor. Carbamazepine is commonly prescribed as first-line therapy for patients with trigeminal neuralgia. Gabapentin has been recently marketed for the management of neuropathic pain syndromes, particularly diabetic neuropathy and postherpetic neuralgia. Valproic acid (sodium valproate), in the form of divalproex sodium, is approved for migraine prophylaxis. Primidone can be considered a valuable option for the treatment of essential tremor. AEDs are also used to treat psychiatric conditions, in particular bipolar disorder. So far, the most commonly utilized AEDs in the treatment of this disorder have been carbamazepine and valproic acid, which have showed an antimanic efficacy and a probable long-term, mood-stabilizing effect in many bipolar patients, including those refractory or intolerant to lithium. The availability of a new generation of AEDs has broadened the therapeutic options in bipolar disorder. Lamotrigine, oxcarbazepine, gabapentin and topiramate appear to be promising in the treatment of refractory bipolar disorder, as a monotherapy as well as in combination with traditional mood stabilizers. In addition, newer AEDs appear to have a more favourable tolerability and drug interaction profile as compared to older compounds, so thus improving compliance to treatment.