Electron capture detection of oxybutynin in plasma: precolumn derivatization approach and application to a pharmacokinetic study

摘要

Oxybutynin is an antimuscarinic agent used for the treatment of an overactive bladder. Because of its poor chromophore, it is difficult to determine oxybutynin by HPLC-UV analysis The difficulty increases when the analysis involves a complex biological matrix like plasma. Precolumn derivatization with trifluoroacetic anhydride followed by GC separation and ECD was used to solve this problem. The developed GC-ECD method had good linearity in the concentration range 2-20 ng ml~(-1) with a correlation coefficient of 0.9959. The accuracy and sensitivity for the determination of the halogenated derivative by this method was better than that for GC-MS. NMR and mass spectroscopy data confirmed the derivatization reaction. The developed GC-ECD method was used to study the pharmacokinetic parameters of an oxybutynin transdermal patch (36 mg/39 cm~2) and oxybutynin gel (10% w/w). The C_(max), T_(max) and AUC_(0-96) values for the oxybutynin transdermal patch and oxybutynin gel were equivalent.