Medication Update

Christy L. Collard, PharmD, Department of Primary Care, Ralph H. Johnson VA Medical Center, Charleston, SC.

South Med J. 2001;94(11) 

In This Article

Potassium-Sparing Diuretics

Mode of Action

Amiloride and triamterene interfere with the sodium-potassium exchange at the distal convoluted tubule of the kidney. Spironolactone acts as an aldosterone antagonist. Aldosterone promotes sodium and water retention. By blocking the actions of aldosterone, spironolactone prevents increases in fluid volume.


Hypersensitivity to the particular potassium-sparing diuretic. Renal dysfunction, including anuria, elevated serum creatinine, and elevated BUN. Elevated serum potassium levels or potassium supplementation. Triamterene should not be used in patients with severe hepatic disease.

Adverse Effects

Hyperkalemia is a common side effect of these medications. GI disturbances, including nausea, vomiting, diarrhea, anorexia can occur. Triamterene and spironolactone have been known to cause impotence and sexual dysfunction. Spironolactone may precipitate gynecomastia or an SLE-like syndrome.

Drug-Drug Interactions

May experience synergistic effects on potassium elevation with the use of ACE inhibitors, cyclosporine, tacrolimus, and other potassium-sparing diuretics. Concomitant use of NSAIDS may result in decreased diuretic effectiveness and increased potassium levels secondary to decreased synthesis of renal prostaglandins. Decreased clearance of digoxin, lithium, and metformin may result in elevated serum levels of these drugs. Increased metformin levels may increase the risk of developing lactic acidosis. Use with caution in patients taking dofetilide, as there is an increased risk of cardiotoxicity (QT prolongation, torsades de pointes) secondary to competition for the renal cation transport system. Warfarin may have a decreased anticoagulant effect secondary to diuresis-induced concentration of clotting factors.

Drug-Food Interactions

Amiloride and triamterene should be taken with food to help decrease GI disturbances. Absorption of spironolactone is enhanced when taken with food.

Available Agents

amiloride: Midamore.
triamterene: Dyrenium.

spironolactone: Aldactone.

Recommended Dose

Depends upon the agent chosen.

Dosage Forms Available

Available in many different dosage strengths.




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