Potassium-sparing diuretics: spironolactone v. triamterene and amiloride

Spironolactone (Aldactone-A),1 triamterene (Dytac)2 3 and amiloride (Midamor)2 are all potassium-sparing diuretics which we have reviewed separately. Spironolactone is a steroid which competitively antagonises aldosterone in the distal renal tubule; triamterene and amiloride directly affect electrolyte transport in the distal tubule without antagonising aldo-sterone. However, the ultimate effects of these drugs are quite similar, and it is not clear whether they should be regarded as interchangeable or whether their uses should differ.