Mannitol

Mannitol is a sugar alcohol or a polyol originally isolated from manna. It is also commonly referred as Mannite or Manna sugar and similar to xylitol or sorbitol. Commonly a substance such as sodium bicarbonate is added to adjust its pH as it tends to lose a hydrogen ion in aqueous solution and causes the solution to become acidic. Mannitol has a negative heat solution and thus can give a cooling effect or fresh feeling to the product; it is commonly used in breath freshening candies. Mannitol can be used by diabetics as a sweetener as it does not affect the blood sugar and insulin levels.

People with diabetes can thus have a wide variety of foods to choose and satisfy their sweet tooth. Mannitol is occasionally used as an adulterant or cutting agent for illicit drugs like heroin or methamphetamines. When mannitol is used for this purpose it is often referred as baby laxative in many films or television shows depicting drug culture. Mannitol is sometimes sold as laxative for children (in larger doses more than 20 gm it acts as a laxative), as due to its sweet taste children consume it easily.

Clinically mannitol is used as a treatment to reduce marginally raised intracranial pressure until more definitive treatment is given (the use of mannitol in this area is currently under controversy). It is believed that mannitol is filtered by glomerulus of the kidney when administered intravenously but there is decrease in water and sodium reabsorption due to its osmotic effects (as it is incapable of being reabsorbed from the renal tubule). Thus mannitol decreases the extra cellular fluid volume by increasing water and sodium excretion.

Mannitol can temporarily shrink the tightly coupled endothelial cells that make up the blood brain barrier, thus it helps to open the blood brain barrier and in turn helps in the delivery of various drugs directly to the brain (helpful in the treatment of Alzheimer’s disease). Mannitol cannot cross biological membranes as it is a non permeable molecule. As it is readily absorbed in blood it is sometimes used to encapsulate a sharp object while it’s passing through the venous system (by the time it reaches its destination the sharp object will be exposed). During a cardiopulmonary bypass mannitol is commonly used in the circuit prime of a heart lung machine. While a patient is on a bypass, the presence of mannitol helps to preserve renal function during the times of low blood flow and pressure. This is done by preventing the endothelial cells in the kidney to swell, which may have otherwise reduced the blood flow and resulted in cell damage. Mannitol is also used for the diagnostic test for airway hyper responsiveness and is being developed by Australian pharmaceutical company for the treatment of bronchiectasis and cystic fibrosis.

Submitted on January 16, 2014