Starch · Sweeteners
Mannitol
The cool, smooth isomer of sorbitol.
Mannitol is an isomer of sorbitol, produced by hydrogenation of fructose. It is a white, odourless substance, available in either granular or powder form. Mannitol has a subtle taste — distinctively pleasant, slightly sweet and cool — with a smooth mouth-feel that is not gritty. The sweetness is about half that of sucrose.
Mannitol neither adds moisture nor contributes to moisture pick-up, thereby eliminating a common cause of degradation of therapeutic actives. It is not self-degradable, nor does it degrade actives which might react with sugars.
Since mannitol has a negative heat of solution, it is used as a sweetener in breath-freshening candies, the cooling effect adding to the fresh feel. Like sorbitol, mannitol is used as a sweetener for people with diabetes. Its inertness and freedom from moisture make it a desirable base in conventional tablets containing moisture-sensitive drugs, and a diluent for many sensitive drugs and vitamins.
Pharmaceutical use
Mannitol is used mainly to reduce intracranial pressure and to treat patients with oliguric renal failure. It is administered intravenously and is filtered in the kidney. Given as a hypertonic solution, it increases distal tubule delivery of Na+ and water, resulting in increased urine formation.
Mannitol can also be used to open the blood-brain barrier by temporarily shrinking the tightly coupled endothelial cells that make up the barrier. This makes mannitol indispensable for delivering various drugs directly to the brain — for example in the treatment of Alzheimer’s disease.