Excretion of N1-Methylnicotinamide and the 6-Pyridone of N1-Methylnicotinamide in Urine of Human Subjects.

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Abstract
Essentially normal subjects maintained for short periods on diets low in nicotinamide and tryptophan excrete approx. 3 mg. of N''-methylnicotinamide (Nl-Me) and 5 mg. of pyridone per day. Following an oral 50 mg. test dose of nicotinamide, the avg. increase in excretion of N1-Me is 5.5 mg. and that of pyridone, 23.4 mg. The excretion of Nl-Me following the test dose rises rapidly during the first 4 hrs. and decreases to basal levels within 24 hrs.; pyridone is excreted more slowly the first few hrs. but appears in large amts. later in the day. After graded doses of nicotinamide, the excretion of pyridone increases more rapidly than does that of Nl-Me. In subjects with pellagra, the excretion of these metabolites is lower both on standard diets and following admn. of small doses of nicotinamide. These data suggest procedures that may be of use in evaluating niacin nutrition.