Osmotic diuretic

An osmotic diuretics are a diuretics which are freely filtered at the glomerulus and subsequently undergo limited reabsorption. They are relatively pharmacologically inert substances, and are given intravenously. They increase the osmolarity of blood and renal filtrate. The prototypical osmotic diuretic is mannitol. Other examples include glycerol, urea, and isosorbide.

Osmotic diuretics work chiefly by expanding extracellular fluid and plasma volume, thereby also increasing renal blood flow. This washes out solutes that maintain the cortical medullary gradient in the kidney, resulting in impaired osmotic urine concentrating ability in the loop of Henle. Osmotic diuretics can be used medically to improve GFR in acute kidney failure, and to reduce intracranial pressure and intra-ocular pressure as well as to promote prompt removal of renal toxins.