Effects of amiloride on plasma and total body potassium, blood pressure, and the renin‐angiotensin‐aldosterone system in thiazide‐treated hypertensive patients

Total body potassium content, plasma potassium concentration, blood pressure, and plasma concentrations of renin, angiotensin II, and aldosterone were measured in patients with essential hypertension after a run‐in period of 8 wk on a regimen of hydrochlorothiazide (median dosage 75 mg/day). Patients were then randomly assigned to continued hydrochlorothiazide therapy (group I) or to receive adjunctive treatment with amiloride (group II, median dosage 15 mg/day or 5 mg per 25 mg hydrochlorothiazide) for the following 3 mo. There were no changes in group I patients during 3 mo on hydrochlorothiazide in plasma potassium, total body potassium content, or the renin‐angiotensin‐aldosterone system. Blood pressure was also unchanged. In group II patients addition of amiloride to hydrochlorothiazide induced a rise in plasma and total body potassium of approximately 15% and 4%. The potassium‐retaining effect was maintained throughout the 12‐wk period, although the maximal changes were observed after 8 wk of treatment. Supine blood pressure did not change, but there was a significant decrease in standing systolic blood pressure. There was a marked rise in plasma concentrations of renin, angiotensin II, and aldosterone. Clinical Pharmacology and Therapeutics (1983) 34, 448–453; doi: 10.1038/clpt.1983.196