HYPONATREMIA ASSOCIATED WITH CARBAMAZEPINE AND OXCARBAZEPINE THERAPY - A REVIEW

Hyponatremia, an electrolyte disturbance usually without clinical sign ificance, may sometimes lead to serious complications when overlooked or not treated appropriately. One cause of hyponatremia, the syndrome of inappropriate antidiuretic hormone (SIADH) secretion, has been asso ciated with some drugs, including car bamazepine (CBZ). Because of its antidiuretic effects, CBZ has been used successfully to treat diabete s insipidus centralis. Possible mechanisms for the antidiuretic effect s of CBZ have been proposed. Altered sensitivity to serum osmolality b y the hypothalamic osmoreceptors appears likely, but an increased sens itivity of the renal tubules to circulating ADH cannot be excluded. CB Z has led to hyponatremia in patients with epilepsy, neuralgia, mental retardation, and psychiatric disorders with a frequency varying from 4.8 to 40%. Oxcarbazepine (OCBZ), which is structurally related to CBZ , has shown similar hyponatremic effects, but whether hyponatremia occ urs more often than with CBZ is not yet clear. Experience with OCBZ is still limited, and there is no definite explanation for a possible di fference in antidiuretic potency. Most patients with CBZ/OCBZ-induced hyponatremia are asymptomatic. In rare cases, water intoxication has b een reported, necessitating treatment discontinuation.