Ingested alcohol undergoes first-pass metabolism (FPM), meaning that a portion of the alcohol is metabolized by enzymes in the gastrointestinal tract and the liver before entering the bloodstream (Figure 1). Blood from the mesenteric veins that supply the gastrointestinal tract is collected by the portal venous system, which, together with the hepatic artery, supplies the liver, allowing alcohol metabolism to occur before the blood returns to the heart. However, the primary site of alcohol’s FPM —whether in the stomach or the liver— has been the subject of ongoing debate. Some investigators consider that the primary site for FPM of alcohol is in the liver and that gastric FPM is negligible (80, 81); others postulate that the stomach is responsible for most FPM of alcohol (82–84).
