Introduction to Osmotic Diuretics
Osmotic diuretics are compounds that increase urine output by non-absorbable solutes. They work primarily in the kidneys' proximal tubules and descending limb of Henle's loop, preventing water reabsorption.
Mannitol: Common Osmotic Agent
Mannitol, the most used osmotic diuretic, is an alcohol derivative of mannose. It is filtered in the glomerulus but not reabsorbed, causing water to follow due to osmotic pressure.
Clinical Uses of Mannitol
Mannitol is employed to reduce intracranial pressure from cerebral edema, intraocular pressure in glaucoma, and to promote diuresis in acute kidney injury and drug overdoses.
Administering Osmotic Diuretics
These diuretics are administered intravenously due to poor gastrointestinal absorption. Dosage must be carefully controlled to avoid rapid shifts in fluid balance, leading to dehydration or hypernatremia.
Mechanism: Osmotic Gradient
Osmotic diuretics create a gradient in the renal tubules. This opposes water reabsorption and enhances excretion. They can also inhibit sodium and chloride reabsorption indirectly.
Potential Adverse Effects
Adverse effects include electrolyte imbalance, dehydration, and overexpansion of extracellular fluid, which can lead to heart failure in susceptible individuals. Monitoring is essential during treatment.
Osmotic Diuretics in Research
Recent studies suggest that osmotic diuretics might protect against kidney injury by flushing out nephrotoxic agents and reducing intratubular cast formation, a surprising potential therapeutic angle.
Where do osmotic diuretics primarily work?
Bladder and urethra
Proximal tubules, Henle's loop
Glomerulus and collecting duct
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