Impaired water homeostasis following mixed carbamazepine and phenobarbital overdose.

Both carbamazepine and phenobarbital are known to have antidiuretic properties when administered chronically. We describe a case of acute impairment of body water homeostasis following mixed drug overdose with carbamazepine and phenobarbital. Serum carbamazepine concentrations correlated with alternating states of diuresis and antidiuresis. We recommend close monitoring of fluid and electrolyte status in carbamazepine overdose.