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A rapid and sensitive liquid chromatography–tandem mass spectrometry method was developed and validated for the quantification of cyclobenzaprine in dog plasma. After extracted with organic solvent, post-treatment samples were separated on an Agela C18 column interfaced with a triple quadrupole tandem mass spectrometer in positive electrospray ionization mode. Multiple reaction monitoring was performed using the transitions of m/z 276.2 → 216.1 and m/z 325.1 → 109.0 to quantify cyclobenzaprine and escitalopram (internal standard), respectively. The mobile phase consisted of acetonitrile: 5 mM ammonium acetate: formic acid (90:10:0.01, v/v/v) at a flow rate of 0.3 ml/min. The total analysis time was 2.4 min. The method was linear over the concentration range of 0.0200–10.0 ng/ml. The intra- and inter-day precision was within 12.8% in terms of relative standard deviation (RSD%) and the accuracy within 5.6% in terms of relative error. This method was successfully applied in a pharmacokinetic study of extended-release cyclobenzaprine in dogs.

The aim of this study was to investigate the effect of backing films on transdermal delivery of cyclobenzaprine patch. Different backing films were chosen to prepare the cyclobenzaprine transdermal patch. The cumulative amount of cyclobenzaprine released from different patches was evaluated in vitro. To investigate the interaction between cyclobenzaprine and backing films, the partitioning experiments and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were performed. The cumulative amount of cyclobenzaprine released from the patch with Cotran? 9700 as backing film was less than that of other patches with different backing films. Furthermore, the cumulative amount of cyclobenzaprine released from the patch with Cotran? 9700 as backing film decreased significantly after 7 d storage at room condition. The partitioning experiments indicated a strong adsorption of cyclobenzaprine onto the Cotran? 9700, which could explain the decrease of cumulative amount of cyclobenzaprine released from the patch with Cotran? 9700 as backing film. According to the ATR-FTIR results, there was no interaction between Cotran? 9700 and cyclobenzaprine. The effect of backing films on the release behavior of cyclobenzaprine transdermal patch was attributed to the adsorption of cyclobenzaprine onto the Cotran? 9700. [ABSTRACT FROM AUTHOR]