Assay of α-difluoromethylornithine in body fluids and tissues by automatic amino-acid analysis

A procedure is described for the measurement of DL-alpha-difluoromethylornithine (DFMO), a selective irreversible inhibitor of ornithine decarboxylase, in biological specimens. The drug is separated from other amino acids with a commerical amino-acid analyser and detected by formation of its alkylthio-isoindole derivative with o-phthalaldehyde. DFMO concentrations of 0.1 nmol can be determined in a sample volume of 100 microliter. The assay has been used to determine the half-life of DFMO in serum of several species and the relationships between serum and tissue concentrations.