Sucrose osmotic diuretic

The osmotic diuretics (e.g. mannitol, sucrose, urea and glycerol) are agents that are filtered freely in the glomeruli, reabsorbed poorly in the tubules and pharmacologically inert. As sodium and water are reabsorbed in the proximal tubule and the loop of Henle, the osmotic diuretics are... 

Mannitol is widely distributed in nature and occurs in the exudates of many plants. It has about half the sweetness of sucrose. Clinically, mannitol is administered intravenously as an osmotic diuretic in patients with acute renal failure. It is not metabolized appreciably, is filtered by the glomerulus, and is not reabsorbed by the tubules hence, it is excreted in urine (Chapter 39). The nonreabsorbable solute holds water, limits back-diffusion, and thus maintains urine volume in the presence of decreased glomerular function. Intravenous mannitol is also used to relieve an increase in pressure and in volume of cerebrospinal fluid. 

Polyols, such as mannitol, sorbitol, and isosorbide, provide this effect. Sugars, such as glucose and sucrose, also can have a diuretic effect by this mechanism. Although not a polyol, urea has a similar osmotic effect and has been used in the past as an osmotic diuretic. 

Mannitol is the agent most commonly used as an osmotic diuretic. Sorbitol also can be used for similar reasons. These compounds can be prepared by the electrolytic reduction of glucose or sucrose. 

On the other hand, borohydride reduction of the ketose o-fructose will give a mixture of o-glucitol and its epimer, D-mannitol. A better approach to D-mannitol would be reduction of the aldose D-mannose. o-Glucitol (sorbitol) is found naturally in the ripe berries of the mountain ash (Sorbus aucuparia), but is prepared semi-synthetically from glucose. It is half as sweet as sucrose, is not absorbed orally, and is not readily metabolized in the body. It finds particular use as a sweetener for diabetic products. o-Mannitol also occurs naturally in manna, the exudate of the manna ash Fraxinus ornus. This material has similar characteristics to sorbitol, but is used principally as a diuretic. It is injected intravenously, is eliminated rapidly into the urine, and removes fluid by an osmotic effect. 

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