Sensitive and specific gas chromatographic and extraction method for the determination of orphenadrine in human body fluids.

A gas chromatographic and extraction method for the assay of orphenadrine in plasma and urine has been developed, in which diphenhydramine is used as the internal standard. The procedure involves extraction with isopentane and alkali flame ionization (nitrogen) detection. Orphenadrine N-oxide and N-dealkylated orphenadrine did not interfere with the analysis. Orphenadrine concentrations down to 1 ng/ml can be determined. Application in a pharmacokinetic/bioavailability study is reported.