Amiloride-induced hyponatremia.

We present three aged female patients who fulfil the criteria of a syndrome that we call "amiloride hyponatremia". They became hyponatremic during amiloride + hydrochlorothiazide therapy. They needed diuretic therapy and tolerated well hydrochlorothiazide with potassium supplementation as potassium chloride. Patients with hyponatremia during diuretic therapy for cardiovascular diseases can be allocated to three groups: 1) Patients with edema and water retention due to severe impairment of cardiac function and decreased water clearance. They need diuretic therapy and water restriction. 2) Patients with "normal diuretic hyponatremia". Hypokalemia and extracellular volume contraction seem to be associated with this phenomenon, and the therapy involves discontinuing the necessary diuretic treatment. 3) Patients with "amiloride hyponatremia". They need diuretic treatment and tolerated thiazide therapy, but the hyponatremia can be corrected by changing amiloride to potassium supplementation. "Amiloride hyponatremia" is suggested to be due to a direct effect of amiloride + hydrochlorothiazide on the distal nephrons. The combination amiloride + hydrochlorothiazide must be used cautiously in elderly patients and the possibility of hyponatremia should be born in mind cases of vague symptoms and CNS disturbances.