Mannitol: Indication, Uses and contraindications
Mannitol is a type of sugar alcohol which is also used as a medication. As a sugar, it is often used as a sweetener in diabetic food, as it is poorly absorbed from the intestines. As a medication, it is used to decrease pressure in the eyes, as in glaucoma, and to lower increased intracranial pressure. Medically, it is given by injection. Effects typically begin within 15 minutes and last up to 8 hours
Used for the promotion of diuresis before irreversible renal failure becomes established, the reduction of intracranial pressure, the treatment of cerebral edema, and the promotion of urinary excretion of toxic substances.
Mannitol is used to reduce acutely raised intracranial pressure until more definitive treatment can be applied, e.g., after head trauma.
It may also be used for certain cases of kidney failure with low urine output, decreasing pressure in the eye, to increase the elimination of certain toxins, and to treat fluid buildup.
Intraoperative mannitol prior to vessel clamp release during renal transplant has been shown to reduce post-transplant kidney injury, but has not been shown to reduce graft rejection.
Mannitol acts as an osmotic laxative in oral doses larger than 20 g, and is sometimes sold as a laxative for children.
The use of mannitol, when inhaled, as a bronchial irritant as an alternative method of diagnosis of exercise-induced asthma has been proposed. A 2013 systematic review concluded evidence to support its use for this purpose at this time is insufficient.
Mannitol is commonly used in the circuit prime of a heart lung machine during cardiopulmonary bypass. The presence of mannitol preserves renal function during the times of low blood flow and pressure, while the patient is on bypass.
The solution prevents the swelling of endothelial cells in the kidney, which may have otherwise reduced blood flow to this area and resulted in cell damage.
Mannitol can also be used to temporarily encapsulate a sharp object (such as a helix on a lead for an artificial pacemaker) while it is passed through the venous system. Because the mannitol dissolves readily in blood, the sharp point will become exposed at its destination.
Mannitol is also the first drug of choice for the treatment of acute glaucoma in veterinary medicine. It is administered as a 20% solution intravenously. It dehydrates the vitreous humor and, therefore, lowers the intraocular pressure. However, it requires an intact blood-ocular barrier to work.
Mannitol is contraindicated in people with anuria, congestive heart failure, and active cerebral haemorrhage (except during craniotomy).
Adverse effects include hyponatremia and volume depletion leading to metabolic acidosis