An osmotic diuretic is a diuretic which is freely filtered at the glomerulus and subsequently undergoes limited reabsorption. Osmotic diuretics 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, as well as to promote prompt removal of renal toxins.
Medical uses
Acute kidney failure
Osmotic diuretic may be indicated in management of acute renal failure when GFR is reduced to such an extent that virtually all water and NaCl reabsorption occurs already in the proximal tubule and next to no tubular fluid flow reaches more distal segments of the nephron and urine output ceases. Such a scenario results in deposition of protein onto the luminal surfaces of the tubules which may then subsequently obstruct tubular fluid flow.