Doxepin is a tricyclic antidepressant drug that has proven effective anesthetic and analgesic
activity in oral mucositis when administered as a topical oral rinse. Aimed to study alternative doxepin
formulations for buccal application, we have developed three different quantitative methods to determine
doxepin. Each method was specifically developed for its intended use: in vitro release, ex vivo
permeation or in vivo studies analyzing plasma. Simple, rapid and easy to perform UV-vis spectrophotometry
analysis was chosen for doxepin quantitation in the in vitro release studies with artificial membranes. A reversedphase
HPLC method with UV-vis detection using a C18 column was developed for the quantitative determination of
doxepin permeated across porcine buccal mucosa. Finally, to determine doxepin plasma concentrations in pigs, a HPLCcoupled
with tandem mass spectrometer analytical method with simple sample preparation was developed. The proposed
methods were validated according to ICH guidelines with respect to specificity, linearity, accuracy and precision. Therefore,
the developed methods were found to be precise, accurate and selective which is suitable for the estimation of
doxepin pharmacokinetics and biopharmaceutics parameters.
Keywords: Spectrophotometer, HPLC, HPLC-MS/MS, validation, bioanalysis, doxepin, tricyclic antidepressants.
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