Carbamazepine and hyponatremia in patients with affective disorder.

The authors assessed 20 carbamazepine-treated patients for the development of hyponatremia. None of the patients had readings below 135 meg/liter of sodium before carbamazepine therapy, but five (25%) did have such readings after carbamazepine therapy. Three of these patients developed frank symptoms of hyponatremia within 1-3 months of the start of therapy. In one patient, hyponatremia developed after rechallenge with carbamazepine. The authors suggest that caution be used in prescribing carbamazepine to patients with low or borderline low sodium values.