Water intoxication in epileptic patients receiving carbamazepine.

Reversal by phenytoin of carbamazepine-induced water intoxication: a pharmacokinetic interaction.

“…A negative correlation between plasma sodium, osmolality and serum carbamazepine concentration has been described before in patients with epilepsy and trigeminal neuralgia.' 2 Our original hypothesis that phenytoin may antagonise the antidiuretic effect of carbamazepine was confirmed by the finding that the diuretic response in patients receiving phenytoin in combination was twice as high as in patients receiving equivalent doses of carbamazepine alone. Our data suggest that the difference could be entirely accounted for by a decrease in serum carbamazepine levels during phenytoin therapy.…”

“…Carbamazepine has antidiuretic properties which have been shown to be positively correlated with the concentration of the drug in serum.1 2 Excessive water retention is relatively common at serum concentration values close to the upper limit of the therapeutic range (12 to 42 Amol/l) and may be troublesome in some patients, particularly those receiving the drug for the treatment of epilepsy and trigeminal neuralgia. '-5 Interestingly, water intoxication appears to be more common in patients treated with carbamazepine alone than in those receiving phenytoin in combination2 and reversal of carbamazepineinduced antidiuresis by phenytoin has been recently described in one patient.6 Although in the latter report the mechanism of the interaction was assumed to be pharmacodynamic, that is, related to the inhibitory action of phenytoin on the release of antidiuretic hormone (ADH) from the posterior pituitary,7 8 …”

Antiepileptic Drugs as a Cause of Worsening Seizures

“…VPA, for example, may induce hyperammoniemia by stimulating the renal production of ammonia (134) and/or inhibiting urea synthesis (135), resulting in a toxic encephalopathy characterized by stupor, epileptic seizures, and myoclonus (whose epileptic nature has been questioned). In the case of CBZ, precipitation of seizures may be facilitated by hyponatremia secondary to the antidiuretic action of the drug (136,136). In a recent survey, 8 of 52 patients with CBZ-induced hyponatremia showed a paradoxical increase in seizure frequency, and sodium levels in these patients was significantly lower than in hyponatremic patients with no increase in seizure frequency (1 38).…”

Hyponatraemia during low-dose carbamazepine therapy

“…2 Although hyponatraemia is a well-recognized side-effect of carbamazepine therapy, it has previously been reported only at moderate or high doses and usually after weeks or months of treatment. [3][4][5][6][7][8][9] This paper reports a case of carbamazepine-induced hyponatraemia in a young Nigerian woman being treated for generalized tonicclonic seizures.…”