Angiotensin-converting enzyme inhibitor-induced syndrome of inappropriate secretion of antidiuretic hormone: case report and review of the literature.

Seventeen cases of severe hyponatremia induced by angiotensin-converting enzyme (ACE) inhibitor therapy have been reported in the literature. The mechanism of severe hyponatremia induced by ACE inhibitor is not clear. A 60-year-old white man with a history of idiopathic dilated cardiomyopathy was treated with enalapril, 20 mg daily, that had been started 2 weeks before heart transplantation. The serum sodium level was 138 mmol/L before initiation of enalapril therapy and 127 mmol/L just before cardiac surgery. In the post-heart transplantation period, enalapril therapy was withdrawn for the perianesthesia period, and the serum sodium level increased from 127 to 140 mmol/L. One month later, viral myocarditis developed in the patient and enalapril was reintroduced at 20 mg daily. Two weeks later, natremia decreased. Enalapril was discontinued. Three days later the serum sodium level rose to 140 mmol/L. Severe symptomatic hyponatremia induced by the syndrome of inappropriate secretion of antidiuretic hormone should be considered a rare but possible complication associated with ACE inhibitor therapy.