Rational Use of Diuretics in Cardiovascular Diseases as of April 23, 2001

Rational Use of Diuretics in Cardiovascular Diseases as of April 23, 2001

The more severe the heart failure, the poorer the response to diuretics; increasing the dose does not necessarily enhance efficacy. Using moderate doses frequently may be more effective. If both sodium and potassium levels are low, distal diuretics are less effective. Distal diuretics act on the distal part of the renal tubules (distal convoluted tubule), often having a potassium-sparing effect, such as spironolactone and amiloride. Common diuretics like furosemide act on the ascending limb of the loop of Henle, while hydrochlorothiazide acts on the cortical portion of the ascending limb. The former is a potent diuretic, while the latter is a moderate one. Acetazolamide is another drug that acts on the distal renal tubules. All of these drugs inhibit sodium reabsorption. For mild heart failure, loop diuretics are preferred; however, in severe cases, loop diuretics are absorbed more slowly, and the more severe the heart failure, the poorer the diuretic's effectiveness—increasing the dose does not help. Long-term low-sodium diets, which result in low sodium and potassium concentrations in urine, make distal diuretics less effective; conversely, when urine has low sodium but high potassium, distal diuretics work better. For patients with refractory congestive heart failure who do not respond well to high-dose loop diuretics, metabolic alkalosis may occur, and treatment with acetazolamide can be effective.