Excretion of organic acids associated with biotin deficiency in chronic anticonvulsant therapy.

Urinary organic acids, known to be elevated in children with biotin deficiency, were determined in 7 epileptics under long-term therapy with anticonvulsants and in three controls. Four patients administered phenytoin, primidone, phenobarbital, or carbamazepine, alone or in combination, had reduced plasma biotin levels (less than 250 ng/l) and an elevated excretion of certain organic acids indicating a possibly decreased activity of propionyl CoA carboxylase (3-OH-propionate, methylcitrate) and 3-methylcrotonyl CoA carboxylase (3-methylcrotonate and the glycine conjugate, 3-OH-isovalerate). Two epileptics receiving sodium valproate alone had normal circulating biotin levels and no changes in level of the investigated urinary acids were found. These findings indicate that the reduced biotin levels seen in epileptics receiving other anticonvulsants than sodium valproate lead to an elevated excretion of certain organic acids in urine.