Partial reversal of carbamazepine-induced water intolerance by demeclocycline

The anti-diuretic action of carbamazepine, before and after concurrent treatment with demeclocycline, has been studied in a single epileptic subject, in whom two episodes of status epilepticus had been associated with excessive fluid intake and hyponatraemia. After addition of demeclocyline, free water clearance, plasma arginine vasopressin concentration and serum osmolality (all appreciably reduced after carbamazepine alone) increased but did not revert to normal. The findings are consistent with direct antagonism by demeclocycline of the enhancing effect of carbamazepine on endogenous ADH activity.