Abstract
Drugs that are administered via the buccal mucosa directly enter the systemic circulation, thereby avoiding hepatic first-pass metabolism. Therefore, this administration route is useful for improving the bioavailability of drugs that are subject to an extensive first-pass effect when delivered orally. For the oral mucosal route of drug administration, various types of dosage forms can be prepared. A sublingual tablet can afford rapid drug absorption and a prompt pharmacological effect; however, the duration of delivery is short owing to the inevitable loss of a large proportion of the administered dose due to swallowing. To avoid such losses, a patch can be formulated that is located on the buccal mucosa of the oral cavity. However, this approach is limited by the thicker dimensions of the buccal membrane compared to the others that line the oral cavity, and constraints impelled by the delivery system itself (the amount of drug reaching the systemic circulation is limited by the area of the mucosa that the patch covers, which, for patient comfort reasons, is relatively small). Direct access to the systemic circulation through the internal jugular vein bypasses drugs from the hepatic first pass metabolism leading to high bioavailability.
