Changes in Nicotinamide Metabolism and Its Bioavailability during Long-Term Administration of a Multivitamin Preparation

SHIBATA Katsumi, ONODERA Michiko, SHIMADA Shun-ichi, YASUDA Kazuto

doi:10.20632/vso.66.5-6_309

We investigated the changes in nicotinamide metabolism and its bioavailability by measuring the urinary excretion of N^1-methylnicotinamide (MNA), N^1-methyl-2-pyridone-5-carboxamide (2-Py), and N^1-methyl-4-pyridone-3-carboxamide (4-Py), and calculating the resulting excretion ratios of (2-Py+4-Py)/MNA and 2-Py/4-Py when healthy men were administered daily 75 mg and 150 mg of nicotinamide as a multivitamin preparation for 44 weeks. During the experimental period, the significant variation such as seasonal change within the same group was not observed. In the ordinary dosage group (75 mg of nicotinamide), the respective urinary excretion of MNA, 2-Py, and 4-Py increased about 4.5, respectively, compared with the basal values. In the double dosage group (150 mg of nicotinamide), the respectively. The urinary excretion of nicotinamide was nearly the limit of detection even when the subjects were administered 150 mg of nicotinamide. The elevated values of the urinary excretion were rapidly returned to the basal values when the administration was ceased. The urinary excretion ratios of (2-Py+4-Py)/MNA and 2-Py/4-Py in the groups of ordinary dosage and double dosage were not observed a difference from the control group during the experimental period. From these results, it was concluded that men can fully metabolize and efficiently utilize the nicotinamide at least up to the intake of 150 mg/day.

Changes in Nicotinamide Metabolism and Its Bioavailability during Long-Term Administration of a Multivitamin Preparation

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