Quantitative determination of aceclofenac and its three major metabolites in rat plasma by HPLC-MS/MS.

We developed a method for the simultaneous quantification of aceclofenac and its three major metabolites in rat plasma. After protein precipitation with acetonitrile including flufenamic acid as an internal standard (IS), aceclofenac, diclofenac, 4'-hydroxyaceclofenac, 4'-hydroxydiclofenac, and the IS were chromatographed on a reverse-phase C18 analytical column. The isocratic mobile phase of acetonitrile/0.1% formic acid (aq; 9:1 [v/v]) was eluted at 0.3 mL/min. Quantification was performed on a triple-quadrupole mass spectrometer using electrospray ionization, and the ion transitions were monitored in selective reaction-monitoring mode. The coefficient of variation in the assay precision was less than 8%, and the accuracy was 92-103%. This method was successfully used to measure the concentrations of aceclofenac and its three major metabolites in rat plasma following the oral administration of a single 20 mg/kg oral dose of aceclofenac.

Simultaneous determination of zolazepam and tiletamine in dog plasma by liquid chromatography coupled to a tandem mass spectrometry.

A mixture of tiletamine, a dissociative anesthetic, and zolazepam, a minor tranquilizer, has been widely used as an anesthetic or an immobilizing agent in a variety of animal species. However, interestingly, their pharmacokinetic behaviors have been published only in polar bears and pigs. In this study, we introduce a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for determining the two drugs in dog plasma. After simple protein precipitation with acetonitrile including midazolam (internal standard), the analytes were chromatographed on a reversed-phase column with a mobile phase of 10 m m ammonium acetate aqueous solution and acetonitrile (1:4, v/v). The accuracy and precision of the assay were in accordance with FDA regulations for the validation of bioanalytical methods. This method was used to measure the concentrations of zolazepam and tiletamine in plasma after a single intramuscular 10 mg dose of each in beagle dogs.