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Diuretics Function: Increase the excretion of Na+ and water Clinical uses a) Treatment for oedema in heart failure
-Vasodilation may be a useful side effect in heart failure- it decreases venous return so reduces ventricular dilation and also decreases peripheral resistance b) Treatment for hypertension
-Reduce circulating volume
-Vasodilation c) Treats cerebral oedema-osmotic diuretics
-Dehydration of inflamed tissue Types
-Pottasium sparing diuretics
-Osmotic diuretics (rarely used) Potency -correlates with site of action, generally earlier they act more potent the drug
-Proximal-tubule diuretics, e.g osmotic diuretics are most potent proximal tubule has large capacity for water reabsorption. But some water is reabsorbed by distal nephron, reducing the overall effect
-Loop diuretics: Furosemide exert a large effect at loop of henle
-Distal tubule diuretics: Thiazides, exert only a mild effect, because relatively little sodium is normally reabsorbed at site of action 1) osmotic diuretics Mannitol
-Infused intravenously, increasing plasma osmolarity- this draws water from oedematous and all other tissues
-Freely filtered at glomerulus so generates a large osmotic potential in the lumen at the proximal tubule, opposing osmotic gradient for paracellular absorption of water
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