Potassium sparing Diuretics (FETT)

Diuretics

Amiloride

SPIRONOLACTONE

Aldosterone receptor antagonist

Spironolactone and eplerenone are aldosterone receptor antagonists.

To remember that Spironolactone, Triamterene, Eplerenone, and Amiloride are K+-sparing, think of STEAK!

Epithelial sodium channel blcoker

Although the molecular pathways differ, both types of potassium-sparing diuretics have very similar clinical effects.

• Aldosterone receptor antagonists (spironolactone, eplerenone)

  • Competitively bind to aldosterone receptors in the late distal convoluted tubule and the collecting duct → inhibition of the effects of aldosterone → decreased Na+ reabsorption and K+ excretion → diuresis

  • Decreased H+ excretion → acidosis

  • Evolving hyperkalemia induces H+/K+-ATPases in all cells to counteract the increase in serum K+ → K+ enters cells in exchange for H+ → amplifies acidosis

  • Spironolactone also acts (nonspecifically) on sex hormone receptors → endocrine side effects (see section “Gonads” in “General endocrinology” for more information about hormonal effects of spironolactone)

• Epithelial sodium channel blockers (triamterene, amiloride): direct inhibition of the epithelial sodium channels (ENaC) in the distal convoluted tubule and the collecting duct → reduced Na+ reabsorption and reduced K+ secretion → diuresis

• Metabolic and electrolyte imbalances, such as hyperkalemia, hyponatremia, and metabolic acidosis, can lead to cardiac arrhythmias

• Gastrointestinal disturbances (nausea, vomiting, diarrhea)

endocrine disturbances

• Men: antiandrogenic effects (e.g., gynecomastia, erectile dysfunction)

• Women: amenorrhea

• Hypertension (especially if hypokalemia is also present)

• Ascites/edema due to congestive heart failure, nephrotic syndrome, or cirrhosis of the liver (mainly spironolactone)

• Hyperaldosteronism (Conn syndrome)

• Nephrogenic diabetes insipidus (amiloride)

• Hypokalemia

• Hyperandrogenic states, e.g., polycystic ovary syndrome (spironolactone)

• Anuria and/or renal insufficiency

• Preexisting hyperkalemia

• Addison disease

• Combination with other potassium-sparing diuretics or potassium supplements

Use with caution in patients with CHF with either of the following:

• GFR < 30 mL/min

• Creatinine ≥ 2.5 mg/dL (men) or ≥ 2 mg/dL (women)

diabetic nephropathy