Potassium Sparing Diuretics

Mechanism of action

• The main potassium sparing diuretic used in clinical practice is spironolactone
  • Competitive antagonist of aldosterone at the aldosterone-dependent sodium-potassium exchanger at the distal convoluted renal tubule
  • Causes increased sodium and water, with retention of potassium (i.e. both diuretic and anti-hypertensive drug)

Indications

• Oedema/Ascites in liver failure or malignancy; nephrotic syndrome; oedema of congestive heart failure
• May also be used as an adjunct in moderate to severe heart failure (in conjunction with an ACEI/ARB and Beta blocker) or resistant hypertension
• Primary hyperaldosteronism

Cautions/Contraindications

• Do NOT give potassium supplementations if a patient is on spironolactone; monitor U&Es regularly and stop if hyperkalaemia is a problem.
• Contraindicated in hyperkalaemia; anuria; Addison’s disease
• Avoid also in acute or severe renal impairment (in renal disease monitor potassium closely)

Side effects

• GI disturbance; hepatotoxicity; malaise; confusion; drowsiness; dizziness
• Gynaecomastia; benign breast tumour; breast pain; menstrual disturbances and changes in libido
• Electrolyte disturbances e.g. hyperkalaemia; hyponatraemia
  • Acute renal failure
  • Hyperuricaemia (gout)
• Rarely, blood disorders e.g. leucopenia, agranulocytosis, thrombocytopenia
• Others include leg cramps, alopecia, rash (including Stevens Johnson sydrome)

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