Diuretics

Potassium sparing

Amiloride

• blocks the epithelial sodium channel in the distal convoluted tubule
• weak diuretic, usually given with thiazides or loop diuretics as an alternative to potassium supplementation (remember that thiazides and loop diuretics often cause hypokalaemia)

Aldosterone antagonists

e.g. spironolactone

• acts in the cortical collecting duct
• indications
  • ascites: patients with cirrhosis develop a secondary hyperaldosteronism. Relatively large doses such as 100 or 200mg are often used
  • heart failure
  • nephrotic syndrom