Biotin catabolism is accelerated in adults receiving long-term therapy with anticonvulsants.

Using serum biotin concentration as the indicator, a previous study reported biotin deficiency resulting from long-term anticonvulsant therapy. However, serum biotin may not be a good indicator of tissue biotin status. Using better indicators of biotin status in anticonvulsant-treated subjects, we found increased urinary excretion of biotin catabolites and 3-hydroxyisovaleric acid, an organic acid produced in greater quantities secondary to reduced activity of a biotin-dependent carboxylase. We conclude that anticonvulsant treatment led to increased biotin catabolism and probably to reduced biotin status.