Mannitol is a type of sugar alcohol used as a sweetener and medication. It is used as a low calorie sweetener as it is poorly absorbed by 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 or inhalation. Effects typically begin within 15 minutes and last up to 8 hours. Common side effects from medical use include electrolyte problems and dehydration. Other serious side effects may include worsening heart failure and kidney problems. It is unclear if use is safe in pregnancy. Mannitol is in the osmotic diuretic family of medications and works by pulling fluid from the brain and eyes. The discovery of mannitol is attributed to Joseph Louis Proust in 1806. It is on the World Health Organization's List of Essential Medicines. It was originally made from the flowering ash and called manna due to its supposed resemblance to the Biblical food. Mannitol is on the World Anti-Doping Agency's banned drug list due to concerns that it may mask other drugs. Uses Medical uses In the United States, mannitol is indicated for the reduction of intracranial pressure and treatment of cerebral edema and elevated intraocular pressure. In the European Union, mannitol is indicated for the treatment of cystic fibrosis (CF) in adults aged 18 years and above as an add-on therapy to best standard of care. Mannitol is used intravenously to reduce acutely raised intracranial pressure until more definitive treatment can be applied, e.g., after head trauma. While mannitol injection is the mainstay for treating high pressure in the skull after a bad brain injury, it is no better than hypertonic saline as a first-line treatment. In treatment-resistant cases, hypertonic saline works better. Intra-arterial infusions of mannitol can transiently open the blood–brain barrier by disrupting tight junctions. 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 build up. 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