Pharm 101: Spironolactone


Potassium-sparing diuretic

  • Synthetic steroid
  • Competitive antagonist to aldosterone at the mineralocorticoid receptor
    • Reduces K secretion –> reduces Na absorption in collecting duct
    • Also inhibits H secretion in parallel
  • Slow onset and offset of effect
  • Hepatic metabolism to active metabolites canrenone and 7-alpha-spirolactone (long half lives of 12-20 hours)
  • Duration of action 24-48 hours
Clinical uses
  • Primary hyperaldosteronism
  • Secondary hyperaldosteronism:
    • CCF
    • Cirrhosis
    • Nephrotic syndrome
Adverse effects
  • Hyperkalaemia
  • Hyperchloraemic metabolic acidosis:
    • Due to inhibition of H secretion in parallel with K secretion
  • Gynecomastia:
    • Potent inhibitor of androgen receptor
  • Potassium supplements
  • Dose adjustment in liver failure
  • NSAIDs:
    • Action of aldosterone antagonists depend on renal prostaglandin production

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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