Examination of stability of anticonvulsants in a protease solution and assay of anticonvulsants in hairs.

For analyzing the concentrations of drugs in hairs, a new method of digestion of hairs with Biopurase, a protease obtained from Bacillus subtilis, was examined. The concentrations of drugs in hairs were then determined in order to examine the usefulness of the protease for the digestion of hairs. The stability of five anticonvulsants in the protease solution was maintained over a 12-h period. In the clinical tests, the concentrations of the drugs in hairs obtained from patients who were taking anticonvulsants for a long time were determined. The concentration of phenobarbital in hairs in 10 patients taking phenobarbital ranged from 194 to 5020 ng/10 mg with a mean of 578 ng/10 mg, and the concentration of phenytoin in hairs in 6 patients taking phenytoin ranged from 44 to 299 ng/10 mg with a mean of 115 ng/10 mg. From these results, the transfer of phenobarbital and phenytoin from circulating blood into hairs was confirmed, and the usefulness of Biopurase for the digestion of hairs was proved.