An interaction between haloperidol and carbamazepine in a patient with cerebral palsy.

A 37-year-old woman with cerebral palsy and a rapid cycling bipolar affective disorder developed drowsiness and slurred speech when being treated with a combination of haloperidol and a low dose of carbamazepine. This effect occurred twice but did not appear when the patient was given carbamazepine alone at much higher doses. This suggests that some patients who appear intolerant of carbamazepine may still benefit from this drug if concomitant haloperidol therapy is ceased.