An osmotic diuretic is a type of diuretic that inhibits reabsorption of water and Na. They are pharmacologically inert substances that are given intravenously. They increase the osmolarity of blood and renal filtrate.
Two examples are mannitol and isosorbide.
In the nephron, osmotic diuretics act at the portions of the nephron that are water-permeable.
Osmotic diuretics works by expanding extracellular fluid and plasma volume, therefore increasing blood flow to the kidney. This washes out the cortical medullary gradient in the kidney. This stops the loop of Henle from concentrating urine, which usually uses the high osmotic and solute gradient to transport solutes and water.
These agents can also act at other parts of the body. For example, they can be used to reduce intracranial and intra-ocular pressure.
Read more about Osmotic Diuretic: Physiological Working of Osmotic Diuretics
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