An improved cryopreservation method for porcine buccal mucosa in ex vivo drug permeation studies using Franz diffusion cells.

The use of isolated animal models to assess percutaneous absorption of molecules is frequently reported. The porcine buccal mucosa has been proposed as a substitute for the buccal mucosa barrier on ex vivo permeability studies avoiding unnecessary sacrifice of animals. But it is not always easy to obtain fresh buccal mucosa. Consequently, human and porcine buccal mucosa is sometimes frozen and stored in liquid nitrogen, but this procedure is not always feasible. One cheaper and simpler alternative is to freeze the buccal mucosa of freshly slaughtered pigs in a mechanical freezer, using DMSO and albumin as cryoprotective agents. This study compared the ex vivo permeability parameters of propranolol hydrochloride through porcine buccal mucosa using a Franz diffusion cell system and HPLC as detection method. The freezing effects on drug permeability parameters were evaluated. Equally histological studies were performed. Furthermore, the use of the parameter transmucosal water loss (TMWL) as an indicator of the buccal mucosa integrity was evaluated just as transepidermal water loss (TEWL) is utilized for skin integrity. The results showed no difference between fresh and frozen mucosal flux, permeability coefficient or lag time of propranolol. However, statistical significant difference in TMWL between fresh and frozen mucosa was observed.

A comparative ex vivo drug permeation study of beta-blockers through porcine buccal mucosa.

Apparent permeability coefficients (kp) of a series of beta-blockers: acebutolol, atenolol, labetalol, metoprolol, oxprenolol and propranolol, through porcine buccal mucosa were determined. The aim of the study was to determine the permeation parameters (apparent permeability coefficient, kp; flux, J; and lag time, TL) as a measure of the intrinsic permeability of porcine buccal mucosa to these drugs, in order to predict the efficacy of their possible administration through human buccal mucosa. A positive linear correlation was observed between the apparent permeability coefficient, kpand the partition coefficient, P. Oxprenolol and propranolol are the drugs that presented the highest values of kp: 0.3231×10(2) cm/h and 0.5666×10(2) cm/h, respectively. Multiple linear regression (MLR) using least square estimation was performed on the data set with logkpas dependent variable and the descriptors as predictor variables. The potential systemic capacity after a buccal administration was predicted by estimating the plasma concentrations at steady-stated (Css). Considering the entire process of permeation ex vivo, propranolol and oxprenolol would seem to be the best candidates for administration through the buccal mucosa.