TAILIEUCHUNG - Chapter 071. Vitamin and Trace Mineral Deficiency and Excess (Part 5)

Pellagra: Treatment Treatment of pellagra consists of oral supplementation of 100–200 mg of nicotinamide or nicotinic acid three times daily for 5 days. High doses of nicotinic acid (2 g/d in a time-release form) are used for the treatment of elevated cholesterol and triglyceride levels and/or low high-density lipoprotein (HDL) cholesterol level (Chap. 350). Toxicity Prostaglandin-mediated flushing due to binding of the vitamin to a G protein–coupled receptor has been observed at daily doses as low as 50 mg of niacin when taken as a supplement or as therapy for dyslipidemia. There is no evidence of toxicity from niacin derived from. | Chapter 071. Vitamin and Trace Mineral Deficiency and Excess Part 5 Pellagra Treatment Treatment of pellagra consists of oral supplementation of 100-200 mg of nicotinamide or nicotinic acid three times daily for 5 days. High doses of nicotinic acid 2 g d in a time-release form are used for the treatment of elevated cholesterol and triglyceride levels and or low high-density lipoprotein HDL cholesterol level Chap. 350 . Toxicity Prostaglandin-mediated flushing due to binding of the vitamin to a G protein-coupled receptor has been observed at daily doses as low as 50 mg of niacin when taken as a supplement or as therapy for dyslipidemia. There is no evidence of toxicity from niacin derived from food sources. Flushing always starts in the face and may be accompanied by skin dryness itching paresthesia and headache. Premedication with aspirin may alleviate these symptoms. Flushing is subject to tachyphylaxis and often improves with time. Nausea vomiting and abdominal pain also occur at similar doses of niacin. Hepatic toxicity is the most serious toxic reaction due to niacin and may present as jaundice with elevated aspartate aminotransferase AST and alanine aminotransferase ALT levels. A few cases of fulminant hepatitis requiring liver transplantation have been reported at doses of 3-9 g d. Other toxic reactions include glucose intolerance hyperuricemia macular edema and macular cysts. The upper limit for daily niacin intake has been set at 35 mg. However this upper limit does not pertain to the therapeutic use of niacin. Pyridoxine Vitamin B6 Vitamin B6 refers to a family of compounds including pyridoxine pyridoxal pyridoxamine and their 5 -phosphate derivatives. 5 -Pyridoxal phosphate PLP is a cofactor for more than 100 enzymes involved in amino acid metabolism. Vitamin B6 is also involved in heme and neurotransmitter synthesis and in the metabolism of glycogen lipids steroids sphingoid bases and several vitamins including the conversion of tryptophan to niacin. .

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