Learning Objective
Describe the mechanism of action of osmotic diuretics and identify their primary sites and effects in the nephron.
Mechanism of Action
Inhibit water reabsorption throughout the nephron
PCT → Descending limb of Loop of Henle → Collecting duct
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Create an osmotic force
Filtered mannitol remains in the tubular lumen
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Pulls water into the lumen
Reduces passive water reabsorption.
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Increase urine volume (massive diuresis)
Causes rapid expansion of tubular fluid → strong diuretic effect
