What is the mechanism of action for potassium sparing diuretics?
Sythetic Aldosterone Antagonists - competes with aldosterone at renal receptor sites (Aldosterone normally stimulates Na+ reabsorption & K+ elimination at the distal tubule)
Causes Na+ elimination & K+ reabsorption
What are the therapeutic uses for Potassium sparing diuretics?
Improve morbidity & mortality in left ventricular systolic dysfunction (CHF with ejection fraction <40%); slows CHF disease profession.
Used in combination with thiazides or loops to help retain K+ & prevent hypokalemia.
Reduce portal vein HTN in liver failure pts with ascites.
How powerful are potassium sparing diuretics?
Not powerful enough as a diuretic to be used alone to treat edema.
Can be added when pt has resistant HTN (where pts are already on 3 or more drugs)
What is eplerenone generally reserved for & why?
Eplerenone is generally reserved for pts experiencing sex hormone-related side effects of spironolactone due to its increased cost ($115/mo as compared to $20/mo)
What are the adverse effects of potassium sparing diuretics?
Hyperkalemia (Can be life-threatening)
Spironolactone, since it chemically resembles some sex steroids, may cause gynecomastia (10%) in men & menstrual irregularities & deepening of voice in females. Eplerenone is more selective & does not cause these side effects.
What are the contraindications/precautions of using potassium sparing diuretics?
Serum K+ >5.5 mEq/L at initiation or CrCl <30 mL/min.
Use extreme caution if pts are receiving K+ supplements, ACE-I, ARBs, or using salt substitutes.
Eplerenone use is contraindicated with powerful CYP3A4 inhibitors such as macrolides, ketaconazole, itraconazole & others.
What is the mechanism of action for amiloride & triamterene?
NOT aldosterone antagonists.
Act directly in the distal renal tubule to inhibit the Na+ reabsorption & K+ elimination that is normally stimulated by aldosterone.
What are the therapeutic uses for amiloride & triamterene?
Mostly used to help retain K+ & prevent hypokalemia; NOT used in management of CHF or portal vein HTN like spironolactone