mannitol

Mannitol is a sugar alcohol, classified as a hexitol, that occurs naturally in small amounts in some plants and seaweeds and is produced commercially for medical and pharmaceutical uses. It is a white, crystalline, highly polar solid that is very soluble in water.

Industrial production typically involves catalytic hydrogenation of glucose- or fructose-containing streams derived from starches. The resulting compound is mannitol, a stable and inert osmotic agent used in medicine, pharmacy, and research.

The main medical uses of mannitol are as an osmotic diuretic and as a diagnostic tool. Intravenous mannitol is used to reduce intracranial and intraocular pressure by drawing water out of edematous tissue into the bloodstream, where it is subsequently excreted by the kidneys. It is also employed in some settings to assess renal function and to expand plasma volume in specific clinical situations. Orally administered mannitol is used as an osmotic laxative to relieve constipation or to prepare the bowel before procedures.

Pharmacologically, mannitol is not metabolized by humans. It increases plasma osmolality, causing water to move from intracellular and interstitial compartments into the intravascular space, after which it is filtered by the kidneys and eliminated in the urine. The diuretic effect and osmotic action depend on intact renal function and adequate blood flow.

Adverse effects can include dehydration, electrolyte imbalances (such as hyponatremia or hyperkalemia), and hypotension. It should be avoided in patients with anuria, significant renal impairment, heart failure, or severe dehydration. Careful monitoring of fluid status and electrolytes is essential during use.

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