Quantitative determination of fenclorac in serum.

A spectrophotometric method for the analysis of fenclorac and its metabolite, 3-chloro-4-cyclohexylbenzeneglycolic acid, in human serum was developed. The parent compound represented at least 90% of the total species present in blood; the metabolite was present to the extent of about 10%, primarily in the elimination phase. The basic procedure consists of extraction of both compounds from serum, further extraction to remove interfering substances, alkaline conversion of fenclorac to the alpha-hydroxy acid metabolite, oxidation of this metabolite to the corresponding benzaldehyde derivative, and spectrophotometric measurement of the absorbance of the aldehyde at 252 nm. A comparison of serum concentrations obtained by this method with concentrations calculated from 14C-data following oral administration of 1-14C-fenclorac to eight normal adult volunteers indicated a 90% correlation between methodologies over a range of 1.4-25.5 microgram of fenclorac/ml of serum.