Buccal (BUC) administration
Administration of a drug by dissolving a tablet against the inside of the cheek, so that drug is absorbed directly into the systemic circulation, thereby avoiding the first pass effect. Typically, a small tablet or pellet would be placed in the cavity between the upper gum and the lining of the cheek, though sprays and water-soluble patches are also used.
Buccal administration is usually used when drugs have very low oral bioavailability, and/or when a rapid response to the drug is required. Any drug administered by the buccal route, but which is swallowed in saliva, would then be subjected to first pass metabolism.
Clinical Context
Understanding where absorption occurs can be important in understanding the purpose of formulations. A sublingual lorazapam tablet can be used to treat a seizure or panic attack as buccal absorption is both rapid and extensive, which is important for a rapid onset of action. Alternatively, when a rapid onset of action is not required, lorazepam can be administered as an oral tablet as it has excellent oral bioavailability.
In contrast, the nitrovasodilator drug nitroglycerin would have extremely low bioavailability if taken orally, as a result of very extensive first pass metabolism. By administering nitroglycerin as a sublingual tablets or as a buccal spray, we can achieve a rapid therapeutic effect while avoiding first pass metabolism.
