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Alcohols are saturated organic compounds that contain at least one hydroxyl group (OH). The general formula of alcohol is CnH2n+1OH. Alcohol can be of many types. In this article, we will discuss the mannitol. This article will cover all important points like what is mannitol, mannitol structure, mannitol uses, mannitol action and mannitol injection uses. 


What is Mannitol?

Mannitol is a six-carbon, linear, simple, and polyhydroxy sugar alcohol. It is a low molecular weight compound. Its chemical formula is C6H14O6.  It gets easily filtered through the glomerulus but it can not be reabsorbed in the renal tubule of the kidney. 


Mannitol Structure

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Mannitol is an isomer of sorbitol. The only difference in the structure of mannitol from sorbitol is the orientation of the hydroxyl group on the second carbon. All the carbons present in the mannitol are sp3 hybridized. All bonds present in the mannitol are sigma bonds.


Comparison of Sorbitol and Mannitol.

Sorbitol

Mannitol

Hydroxyl group at second carbon is present out of the plane.

Hydroxyl group at second carbon is present behind the plane.

Less sweet than sugar.

Sweeter than sugar.

Contains 2.6 calories/gram.

Contains 1.6 calories/gram.

Mainly used as a sugar substitute.

Mainly used as a medicine.


Properties of Mannitol

  • The molar mass of mannitol is 182.172 g/mol.

  • The density of mannitol is 1.489 at 68°F.

  • The boiling point of mannitol is 563°F at 3.5 mm Hg.

  • The melting point of mannitol is 333°F. 

  • It is an odourless compound.

  • It occurs naturally in white crystalline or in granule form.

  • It is sweet in taste.

Mannitol Action 

  • Mannitol is a polyhydroxy compound, which is mildly metabolized by the body. The renal tubule does not have the capacity to absorb it. Therefore, it rapidly gets excreted by the kidney, when mannitol injection is used and poorly absorbed when taken orally.  

  • Mannitol, when ingested orally, passes through the intestine and excreted in the feces as the small intestine is not able to absorb it properly. Therefore, it does not affect blood sugar and can be used as a sweetener for the diabetic patient.

Mannitol Uses

  • Mannitol is used for promoting diuresis for acute renal failure.

  • Mannitol is used for increased intracranial pressure.

  • Mannitol is used for the excretion of toxic material.

  • Mannitol is used as a sweetener for diabetic food products.

  • Mannitol is used for preventing intradialytic hypotension.

  • It is used to measure Extracellular Fluid (ECF) and Glomerular Filtration Rate (GFR).

  • It is used in cardiopulmonary bypass.

Mannitol Injection Uses

Mannitol is used as a medicine. Mannitol infused into a vein or into the urethra. It should never be given subcutaneously. It is infused by health care professionals in a hospital or clinic. The total concentration, dosage, and rate of mannitol administration should be governed by the nature and severity of the condition. The standard adult dose ranges from 50-200 g/day. The rate of infusion is usually adjusted to maintain a urine flow. 


Harmful Effects of Mannitol

  • It can cause dehydration when consumed in excess amounts.

  • At low temperature, it gets precipitated and can damage the vascular organ system.

  • It can cause heart failure.

  • It can cause pulmonary edema.

  • It can cause renal failure.

Did You Know?

  • Mannitol is found in mushrooms, brown algae, and bark of manna trees.  

  • Mannitol lowers the blood pressure. 

  • Mannitol in the intestine for a long time can cause bloating and diarrhoea.  

FAQ (Frequently Asked Questions)

Question: Give Any Five Physical Properties of Mannitol.

Answer: Five physical properties of mannitol are given below

  1. The density of mannitol is 1.489 at 68°F.

  2. The boiling point of mannitol is 563℉ at 3.5 mm Hg.

  3. The melting point of mannitol is 333℉. 

  4. It is an odourless compound.

  5. It occurs naturally in white crystalline or in granule form.

Question: Explain the Use of Mannitol.

Answer: The use of mannitol are given below:

  • Mannitol is used to promote diuresis for renal failure- Mannitol can promote diuresis for acute renal failure to prevent or treat the oliguric phase before irreversible damage.

  • Mannitol is used for increased intracranial pressure- Mannitol constitutes a solute in the plasma, this increases the tonicity of the plasma. Since mannitol cannot cross the intact blood-brain barrier, therefore, it is responsible for increased intracranial pressure.

  • Mannitol is used for the excretion of toxic material- The mannitol is poorly reabsorbed once it gets excreted from the body, it draws extra water with it into the renal collecting ducts.

  • Mannitol is a sweetener for diabetic food products- Mannitol when ingested orally passes through the intestine and excreted in the feces as the small intestine absorbs it poorly. So, it does not affect blood sugar.

  • Mannitol is used to prevent intradialytic hypotension- It raises the serum osmolality. Hence, prevent hypotension.