Absorption from the oral cavity will eventually reach the liver in a second circulation.

• A. Cannot be determined
• B. True
• C. False
• D. Partially true

Answer: (B)

Absorption from the oral cavity is routed either through sublingual/buccal mucosa or by swallowing. Sublingual/buccal absorption delivers the drug directly into systemic circulation, bypassing hepatic first-pass metabolism, while swallowing sends it into the GI tract where it reaches the liver via the hepatic portal vein on first pass. However, any drug that enters the systemic circulation will be part of the body's circulating blood and eventually reach the liver through hepatic arterial and portal venous blood. Because of this, absorption from the oral cavity will eventually reach the liver in the second circulation. The extent of hepatic exposure depends on whether the drug took the sublingual/buccal path or the swallow path, but the liver is encountered in the systemic circulation.