Use of Permeapad® for prediction of buccal absorption: A comparison to in vitro, ex vivo and in vivo method.

The present work explores the usefulness of Permeapad® for prediction of buccal absorption. Permeability studies with the model drug metoprolol were carried out using the Permeapad® barrier at pH values 7.4; 8.5; 9.0, and 9.5. It was confirmed that Permeapad® can withstand these conditions, and as expected, a clear increase in permeability was found with increasing pH. The permeation results across Permeapad® were compared to published in vitro, ex vivo and in vivo studies for the same formulations. Results showed that the permeability of metoprolol using the Permeapad® barrier correlated very well to both in vitro and ex vivo studies, (r(2)=0.98 and 0.97), respectively. Furthermore, excellent in vitro in vivo correlation IVIVC (r(2)=0.98) was obtained when comparing apparent permeability coefficient to the absolute bioavailability of metoprolol administered buccally to mini-pigs. Results indicate that Permeapad® can be used to mimic the buccal absorption of metoprolol as a faster and less laborious method as compared to any of the other mentioned methods.