Erphacea

Uses

Selenium is an ingredient found in a variety of supplements and vitamins.

For the supplementation of total parenteral nutrition to prevent hyposelenemia .

Erphacea is also used to associated treatment for these conditions: Nutritional supplementation

How Erphacea works

Selenium is first metabolized to selenophosphate and selenocysteine. Selenium incorporation is genetically encoded through the RNA sequence UGA . This sequence is recognized by RNA ste loop structures called selenocysteine inserting sequences (SECIS). These structures require the binding of SECIS binding proteins (SBP-2) to recognize selenocystiene. The specialized tRNA is first bound to a serine residue which is then enzymatically processed to a selylcysteyl-tRNA by selenocystiene sythase using selenophosphate as a selenium donor. Other unidentified proteins are required as part of the binding of this tRNA to the ribosome. Selenoproteins appear to be necessary for life as mice with the specialized tRNA gene knocked out exhibited early embryonic lethality .

The most important selenoproteins seem to be the glutathione peroxidases and thioredoxin reductases which are part of the body's defenses againts reactive oxygen species (ROS) . The importance of selenium in these anti-oxidant proteins has been implicated in the reduction of atherosclerosis by preventing the oxidation of low density lipoprotein . Selenium supplementation is also being investigated in the prevention of cancer and has been suggested to be beneficial to immune function .

Toxicity

Oral LD50 of 6700mg/kg in rats . Selenium exposure is teratogenic and can result in fetal death as tested in mice. Chronic toxicity is characterized by hair loss, white horizontal streaking on fingernails, paronchyia, fatigue, irritability, hyperreflexia, nausea, vomiting, garlic odor on breath, and metallic taste . Serum selenium correlates weakly with symtoms. Blood chemistry as well as liver and kidney function are normally unnaffected. Acute toxicity presents as stupor, respiratory depression, and hypotension. ST elevations and t-wave changes characteristic of myocardial infarction may be observed.

Elimination Route

Oral bioavailability of 90% when given as L-selenomethionine . Tmax of 9.17h.

Half Life

Half life was observed to increase with chronic dosing time . For day 1-2 half life was 1.7 days. For day 2-3 half life was 3 days. For day 3-14 half life was 11.1 days.

Elimination Route

Mainly excreted in urine as 1beta-methylseleno-N-acetyl-d-galactosamine and trimethylselenonium . The amount excreted as 1beta-methylseleno-N-acetyl-d-galactosamine plateaus at doses around 2microg after which the amount excreted as trimethylselenonium increases. Some selenium is also excreted in feces when given orally .

Innovators Monograph

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