Mode of action

Loop diuretics:

• act primarily via the co-transport pathway for Na/K/Cl in the ascending loop of Henle. Secondary to reduced sodium reabsorption there is reduced water reabsorption (a passive process) from the distal tubule and collecting duct.
• as a consequence of reduced sodium reabsorption in the ascending loop (where no water absorption occurs) there is reduced free water formation. Sodium reabsorption is inhibited proximal to the distal tubule (potassium secreting site) and the increased sodium load in the distal tubule leads to an increase in potassium secretion.
• furosemide reduces calcium absorption in the loop of Henle
• also increase renal prostaglandin synthesis, which may account for the vasodilator effects on the renal arterioles and systemic veins and helps to explain why NSAIDs attenuate the diuresis (1)

Reference:

1. Prescriber 2004; 15(9):50-6.