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           Niacin (B3)

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Niacin (Vitamin B3): Niacin refers to both nicotinic acid and nicotinamide, which have identical vitamin properties but different pharmacologic activities. Niacin is involved in the production of energy, the synthesis of fatty acids, cholesterol, steroids and the regulation of genes. Nicotinic acid is used as a lipid lowering agent in pharmacologic dosages. Niacin deficiency causes pellagra (dermatitis, diarrhea and dementia), most often seen in alcoholism, malabsorption syndromes, cirrhosis and those receiving total parenteral nutrition.

Toxicity: Nicotinic acid can cause flushing from cutaneous diditation of blood vessels. High dosages (3 grams/day) may cause glucose intolerance, blurred vision, macular edema, and elevated uric acid. Those on high dosages should have liver function tests monitored on a regular basis for liver toxicity.

Tolerable Upper Level: Not determined.

Drug interactions: Use of nicotinic acid in conjunction with calcium channel blockers,alpha1-blockers and nitrate patches may potentiate the hypotensive effects of these drugs. Use of nicotinic acid and alpha-glocosidase inhibitors, sulfonureas, biguanides, and meglitinides may decrease their anti-diabetic effects. Use with warfarin may result in significant increase in prothrombin time. Aminoglycosides, tetracyclines, cephaolsporins and penicillins may deplete B3; Cholestyramine and colestipol may reduce absorption of nicotinic acid. Nicotinamide may increase levels of carbamazepine.



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Last modified: June 04, 2005