Diuretics

Key points

• Loop diuretics (furosemide): inhibit Na⁺-K⁺-2Cl⁻ cotransporter in the thick ascending loop of Henle; side effects — hypokalaemia, hyponatraemia, ototoxicity, gout.
• Thiazides (bendroflumethiazide): inhibit Na⁺-Cl⁻ cotransporter in distal convoluted tubule; side effects — hyponatraemia, hypokalaemia, hypercalcaemia, gout, impaired glucose tolerance.
• Potassium-sparing (spironolactone, amiloride): spironolactone = aldosterone antagonist → gynaecomastia; amiloride blocks ENaC.
• Loop diuretics are more effective than thiazides in significant renal impairment (low GFR).
• Metolazone has synergistic effect with loop diuretics in resistant oedema.