Long-term therapy with carbamazepine: effects on nerve conduction velocity.

Peripheral nerve function was evaluated in 30 epileptic patients on chronic therapy with carbamazepine (CBZ) and 20 healthy controls. The electrophysiological data indicated a mild progressive reduction of both motor and sensory conduction velocity in the patients on long-term treatment with the drug. The impairment of nerve function paralleled the duration of therapy (i.e. 1 through 3 years). CBZ plasma levels were constantly within the therapeutic range. Folic acid levels were below normal in about 50% of the subjects. In the absence of other evidence, the hypothesis cannot be excluded that folate deficiency may have played some role in the development of the peripheral nerve dysfunction.