A comparison of the potassium and magnesium-sparing properties of amiloride and spironolactone in diuretic-treated normal subjects.
1. The relative potencies of amiloride (5 and 20 mg) and spironolactone (25 and 100 mg) for plasma and erythrocyte electrolytes were investigated in a double-blind, randomised, balanced, crossover study in 12 normal men treated concomitantly with hydrochlorothiazide 100 mg daily for 1 week. 2. Participants satisfied an a priori requirement for a fall in plasma potassium concentration of at least 0.5 mmol l-1 after 7 days of treatment with hydrochlorothiazide alone. 3. After hydrochlorothiazide alone, plasma potassium and sodium concentrations fell (P < 0.001). There were associated reductions in erythrocyte sodium (P < 0.01). Plasma magnesium concentration did not change, although erythrocyte magnesium decreased (P < 0.001). 4. Both amiloride and spironolactone attenuated the thiazide-induced fall in plasma potassium (relative potency, amiloride:spironolactone 10:1, 95% confidence interval 6.3-16.2:1). Amiloride but not spironolactone was associated with a dose-related increase in plasma magnesium; a relative potency estimation was precluded. There was little evidence of influences of amiloride or spironolactone on erythrocyte electrolytes. 5. On a weight basis, amiloride is ten times more potent than spironolactone as a potassium-sparing agent in diuretic-treated subjects but neither agent had major effects on erythrocyte potassium. The drugs may have divergent actions on magnesium handling; hydrochlorothiazide alone had no influence on plasma magnesium.
Murdoch
D L
DL
University Department of Medicine and Therapeutics, Western Infirmary, Glasgow.
Forrest
G
G
Davies
D L
DL
McInnes
G T
GT
D000328:Adult; D000450:Aldosterone / Q000097:blood; D000584:Amiloride / Q000009:adverse effects / Q000097:blood / Q000494:pharmacology*; D004311:Double-Blind Method; D004347:Drug Interactions; D004912:Erythrocytes / Q000737:chemistry; D006801:Humans; D006852:Hydrochlorothiazide / Q000009:adverse effects / Q000494:pharmacology*; D007424:Intracellular Fluid / Q000378:metabolism; D008274:Magnesium / Q000097:blood*; D008297:Male; D011188:Potassium / Q000097:blood*; D013148:Spironolactone / Q000009:adverse effects / Q000097:blood / Q000494:pharmacology*
D006852:Hydrochlorothiazide; D013148:Spironolactone; D000450:Aldosterone; D000584:Amiloride; D008274:Magnesium; D011188:Potassium