Serum concentrations of bisnorbiotin and biotin sulfoxide increase during both acute and chronic biotin supplementation.

In addition to the pharmacokinetic interest, serum concentrations of biotin and biotin metabolites are important because biotin in serum might interfere with assays that use avidin-biotin detection systems. With acute and chronic oral administration of biotin the serum concentration of biotin increases. Because of limited specificity of bioassays or avidin-binding assays used in previous studies, the proportion of the increase attributable to biotin metabolites (if any) remains unknown. To address these questions 15 adults consumed 1,200 microg biotin daily for 14 days. Blood samples were obtained before biotin ingestion and at 3 hours after biotin ingestion on the first day ("acute supplementation") and the fourteenth day ("chronic supplementation"). Biotin, bisnorbiotin, and biotin sulfoxide were measured with a chemically specific high-pressure liquid chromatography/avidin-binding assay. Serum concentrations of biotin, bisnorbiotin, and biotin sulfoxide increased approximately fiftyfold with acute supplementation of biotin; each increased further with chronic supplementation. With acute supplementation the proportion of the total attributable to metabolites did not decrease significantly, suggesting that pathways for biotin catabolism are not easily saturated. With chronic supplementation the proportion of the total attributable to metabolites did not increase significantly, suggesting that biotin catabolism was not substantially induced. We conclude that on a mole basis the contribution of biotin metabolites is important, and we provide an estimate of the biotin and biotin metabolite concentration that might be encountered in individuals who self-select large biotin supplements.