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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