title: Fate of excess nicotinamide and nicotinic acid differs in rats.
abstract: Rats administered excess nicotinamide and nicotinic acid were studied to determine the metabolic fate of pharmacological levels of these compounds. When a large amount of nicotinamide (500 mg/kg body wt) was intraperitoneally injected into rats, 32% of the dose was excreted as nicotinamide, 11% as N1-methylnicotinamide (MNA), 10% as nicotinuric acid, 5% as nicotinic acid, 3% as N1-methyl-4-pyridone-3-carboxamide (4-pyr) and 2% as N1-methyl-2-pyridone-5-carboxamide (2-pyr) during d 1 after the injection. Urinary excretion of these compounds gradually decreased with time and returned to normal by d 3. Urinary excretion of nicotinic acid and nicotinuric acid was observed only on d 1. When a large amount of nicotinic acid (500 mg/kg body wt) was intraperitoneally injected into rats, 55% of the dose was excreted as nicotinic acid and 15% as nicotinuric acid during d 1, and no excretion of these compounds was observed thereafter. The increase in excretion of nicotinamide, MNA, 2-pyr and 4-pyr was slight even on d 1. Excretion of nicotinic acid, nicotinuric acid, nicotinamide, MNA, 2-pyr and 4-pyr returned to normal levels on d 2. From these results, the different fates of excess nicotinamide and nicotinic acid are discussed.
authors.affiliation: Department of Food Science and Nutrition, Teikoku Women's University, Osaka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Shibata
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D007274:Injections, Intraperitoneal; D008297:Male; D009536:Niacinamide / Q000378:metabolism* / Q000652:urine; D009539:Nicotinic Acids / Q000378:metabolism* / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D009539:Nicotinic Acids; D009536:Niacinamide