Glucose osmotic diuretic

Osmotic diuretics. Diuretics that are filtered in the glomerulus but cannot be re-absorbed. An example is mannitol. Their presence leads to an increase in the osmolarity of the filtrate to maintain osmotic balance, water is retained in the urine. Glucose, like mannitol, can also behave as an osmotic diuretic. In diabetes mellitus, the concentration of glucose in the blood exceeds the maximum resorption capacity of the kidney glucose remains in the filtrate, leading to the osmotic retention of water in the urine. 

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. 

Readily obt. from glucose. By-prod, of the starch industry obt. by dehydration of Glucitol, G-247. Inexpensive starting material for synthesis. Osmotic diuretic. Used in the treatment of hydrocephalus. Also a chiral modifying agent for asymmetric redn. of ketones. Mp 62-64°. Bp2 160-175°. Mg +44.8 (HjO). 

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. 

Osmotically acting diuretic agents. These are applied in the treatment of intoxication in order to increase the urine volume and accelerate elimination of the poison ( forced diuresis ). The classical example is mannitol. This sugar is quite similar to glucose in structure but does not get metabolized nor reabsorbed from the primary glomerular filtrate in the kidneys. 

HONK coma occurs mostly in elderly, non-insulin dependent diabetics, and develops relatively slowly over days or weeks. The level of insulin is sufficient to prevent ketosis but does not prevent hyperglycacmia and osmotic diuresis. Precipitating factors include severe illness, dehydration, glucocorticoids, diuretics, parenteral nutrition, dialysis and surgery. Extremely high blood glucose levels (above 35 mmol/l. and usually above 50 mmol/l) accompany severe dehydration resulting in impaired consciousness. 

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