Simultaneous high-performance liquid chromatographic determination of lornoxicam and its 5'-hydroxy metabolite in human plasma using electrochemical detection.

A selective and sensitive high-performance liquid chromatographic method with coulometric detection is described for the simultaneous quantitation of lornoxicam, a new oxicam class drug, and its 5'-hydroxy metabolite in human plasma. The two analytes and the internal standard are extracted from plasma at pH 4.0 by liquid-liquid extraction and separated on a C18 column. Absolute detection limits using 100 microliters of plasma are found to be 5 and 10 ng/ml for lornoxicam and 5'-hydroxylornoxicam, respectively. The assay described has been successfully applied to samples from clinical studies.