Effect of Freezing and Type of Mucosa on Ex Vivo Drug Permeability Parameters

The porcine esophageal mucosa has been proposed as a substitute for the buccal mucosa barrier on ex vivo permeability studies mainly due to its large surface area as well as its easier preparation. Therefore, this study compared the ex vivo permeability parameters of two drugs (carmabazepine (CBZ) and triamcinolone acetonide (TAC)) with different permeabilities and physicochemical properties through buccal and esophageal mucosae using a Franz diffusion cell system and HPLC as detection method. The freezing effects on drug permeability parameters were also evaluated by comparing them when fresh and frozen tissues were used. The barrier properties were not affected by the freezing process since the obtained parameters for both drugs were similar in frozen and fresh tissues (buccal and esophageal mucosae). However, an increase of CBZ retention was shown in frozen tissues. Fresh and frozen esophageal mucosae provided higher permeation of TAC than on buccal mucosae while the obtained permeability parameters for CBZ were similar on both mucosae. According to our results, porcine esophageal mucosa could be used as a substitute for buccal mucosa on ex vivo studies involving CBZ but not TAC. Frozen tissues could be used as substitute for fresh tissues in both cases. However, any substitution should be done with care and only if previous tests were performed, because the results could differ depending on the tested drug.