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 ) .
C0033148
primidone
C0031412
phenobarbital