Which organ is the primary site of metabolism via portal circulation after oral administration?

Which organ is the primary site of metabolism via portal circulation after oral administration?

• A. Kidney
• B. Lungs
• C. Liver
• D. Spleen

Answer: (C)

When a drug is taken orally, it is absorbed from the gut and carried via the hepatic portal vein to the liver. There, hepatocytes expose the drug to metabolic enzymes, notably those in the cytochrome P450 family, performing first-pass metabolism before the drug enters the general circulation. This makes the liver the primary site of metabolism for drugs given by mouth, because it is the first major organ encountered by portal-borne compounds. Other organs like the lungs or kidneys can metabolize some drugs, but they do not serve as the main site of metabolism via portal circulation. The spleen has only a minimal role in this process.

When a drug is taken orally, it is absorbed from the gut and carried via the hepatic portal vein to the liver. There, hepatocytes expose the drug to metabolic enzymes, notably those in the cytochrome P450 family, performing first-pass metabolism before the drug enters the general circulation. This makes the liver the primary site of metabolism for drugs given by mouth, because it is the first major organ encountered by portal-borne compounds. Other organs like the lungs or kidneys can metabolize some drugs, but they do not serve as the main site of metabolism via portal circulation. The spleen has only a minimal role in this process.