In vitro permeation of tetramethylpyrazine across porcine buccal mucosa.

Aim: To examine the in-vitro transport route of tetramethylpyrazine (TMP) across porcine buccal mucosa and to investigate the effects of drug concentration, pH in donor chamber, and 1-octanol/buffer partition coefficient on transbuccal permeation.

Methods: In-vitro permeation of TMP through porcine buccal mucosa was studied by using in-line flow through diffusion cells at 37 . The permeability of TMP was evaluated at different donor pH and drug concentration. Permeability of unionized (Pu) and ionized TMP (Pi) was calculated by using the Scientist software.

Results: The steady state flux of TMP increased linearly with the donor concentration (r2=0.96) at pH 7.4. The permeability and the partition coefficient increased with pH. Pu and Pi were 9.05 x 10(-6) cm.s(-1) and 2.99 x 10(-7) cm.s(-1), respectively. The total permeability coefficient increased with the fraction of unionized form.

Conclusion: TMP permeated through buccal mucosa by a passive diffusion process. The partition coefficient and pH dependency of drug permeability indicated that the drug was transported mainly via the transcellular route by a partition mechanism.