Mechanism of Action and Clinical Effects of Metolazone

Pharmacological Action

• The British Journal of Pharmacology reports that metolazone interferes with the renal tubular mechanism of electrolyte reabsorption through inhibition of the sodium-chloride cotransporter in the distal tubule, with a strength of evidence based on pharmacological studies 1
• The drug's action results in increased potassium excretion due to enhanced sodium reabsorption via the epithelial sodium channel (ENaC), requiring increased potassium secretion to maintain electrical neutrality, as reported by the British Journal of Pharmacology 1

Clinical Advantages

• The American College of Cardiology recommends metolazone as it retains efficacy even when glomerular filtration rate falls below 20 mL/min, unlike standard thiazides, with a moderate strength of evidence based on clinical trials 3
• The American Journal of Kidney Diseases notes that metolazone produces marked diuresis through sequential nephron blockade when administered concurrently with furosemide, even in patients refractory to maximum doses of either drug alone, with a high strength of evidence based on clinical studies 4