Determination of amfenac sodium and its metabolites in plasma by GC/MS

Abstract

GC/MS method for determination of amfenac sodium (AMF) and its metabolites (S₁, S₂ and S₃) in plasma was established. The clean-up for the determination of S₁ was efficiently attained by extraction with ethyl acetate under basic condition, and that of AMF, S₂ and S₃ was carried out under acidic condition (AMF was converted into S₁ under acidic condition). S₂ and S₃ were derivatized into the methylester and subjected to GC/MS. The detection limits of AMF and its metabolites were 5 ng/ml each in plasma. The plasma concentrations of AMF and its metabolites after oral administration of AMF capsules to human volunteers were determined by this method.