THIAMINE HYDROCHLORIDE

Absorption

Absorbed mainly from duodenum, by both active and passive processes

Toxicity

Thiamine toxicity is uncommon; as excesses are readily excreted, although long-term supplementation of amounts larger than 3 gram have been known to cause toxicity. Oral mouse LD50 = 8224 mg/kg, oral rat LD50 = 3710 mg/kg.

Physical properties

Free thiamin is unstable because of its quaternary nitrogen; in water, it is cleaved to the thiol form. For this reason, the hydrochloride and mononitrate forms are used in commerce. Thiamin hydrochloride (actually, thiamin chloride hydrochloride) is a colorless crystal that is very soluble in water (1 g/ml, thus making it a very suitable form for parenteral administration), soluble in methanol and glycerol, but practi cally insoluble in acetone, ether, chloroform, and benzene. The mononitrate form is more stable than the hydrochloride form, but it is less soluble in water. It is used in food/feed supplementation and in dry pharmaceutical preparations. Free thiamin is easily oxidized to thiamin disulfide and other derivatives, including thiochrome, a yellow biologically inactive product with strong blue fluorescence that can be used for the quantitative determination of thiamin. Its metabolically active form is thia min diphosphate, also called thiamin pyrophosphate.

Background

Thiamine or thiamin, also known as vitamin B1, is a colorless compound with the chemical formula C12H17N4OS. It is soluble in water and insoluble in alcohol. Thiamine decomposes if heated. Thiamine was first discovered by Umetaro Suzuki in Japan when researching how rice bran cured patients of Beriberi. Thiamine plays a key role in intracellular glucose metabolism and it is thought that thiamine inhibits the effect of glucose and insulin on arterial smooth muscle cell proliferation. Thiamine plays an important role in helping the body convert carbohydrates and fat into energy. It is essential for normal growth and development and helps to maintain proper functioning of the heart and the nervous and digestive systems. Thiamine cannot be stored in the body; however, once absorbed, the vitamin is concentrated in muscle tissue.

Indications

For the treatment of thiamine and niacin deficiency states, Korsakov's alcoholic psychosis, Wernicke-Korsakov syndrome, delirium, and peripheral neuritis.

Definition

ChEBI: Thiamine(1+) is a primary alcohol that is 1,3-thiazol-3-ium substituted by (4-amino-2-methylpyrimidin-5-yl)methyl, methyl and 2-hydroxyethyl groups at positions 3, 4 and 5, respectively. It has a role as a human metabolite, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite and a mouse metabolite. It is a primary alcohol and a vitamin B1. It is a conjugate base of a thiamine(2+).

Pharmacokinetics

Thiamine is a vitamin with antioxidant, erythropoietic, cognition-and mood-modulatory, antiatherosclerotic, putative ergogenic, and detoxification activities. Thiamine has been found to protect against lead-induced lipid peroxidation in rat liver and kidney. Thiamine deficiency results in selective neuronal death in animal models. The neuronal death is associated with increased free radical production, suggesting that oxidative stress may play an important early role in brain damage associated with thiamine deficiency. Thiamine plays a key role in intracellular glucose metabolism and it is thought that thiamine inhibits the effect of glucose and insulin on arterial smooth muscle cell proliferation. Inhibition of endothelial cell proliferation may also promote atherosclerosis. Endothelial cells in culture have been found to have a decreased proliferative rate and delayed migration in response to hyperglycemic conditions. Thiamine has been shown to inhibit this effect of glucose on endothelial cells.

Metabolism

Hepatic