Carbamazepine-induced hyponatremia

Treatment with some drugs may lead to the syndrome of inappropriate antidiuretic hormone secretion (SIADH), the presence of which is more likely in some populations, including people who are elderly or who take diuretics. Resulting drug-induced hyponatremia is often mild and usually resolves following water restriction and withdrawal of the drug. In some patients, however, it may be a potentially fatal condition that is typically asymptomatic until it becomes severe. In this article, we describe the case of a 59-year-old man with arterial hypertension, already treated with hydrochlorothiazide, who presented with hyponatremia after starting administration of carbamazepine. After excluding other common causes of hyponatremia, a diagnosis of SIADH was established, carbamazepine was withdrawn and SIADH treatment introduced. Our study shows that routine assessment of blood electrolytes is reasonable not only in patients receiving diuretics but also in patients treated with other drugs affecting vasopressin secretion.