Which organ is primarily responsible for metabolism of most drugs?

Which organ is primarily responsible for metabolism of most drugs?

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

Answer: (D)

Drug metabolism is mainly carried out by the liver because it contains a high concentration of drug‑metabolizing enzymes in hepatocytes, especially the cytochrome P450 system. These enzymes carry out Phase I and Phase II reactions that transform drugs into more water‑soluble forms, helping them be eliminated more easily. Oral drugs often undergo first‑pass metabolism in the liver, which can significantly reduce their bioavailability before they reach systemic circulation. While the kidneys handle elimination and the lungs metabolize some volatile substances, the liver is by far the primary site for transforming most drugs.

Drug metabolism is mainly carried out by the liver because it contains a high concentration of drug‑metabolizing enzymes in hepatocytes, especially the cytochrome P450 system. These enzymes carry out Phase I and Phase II reactions that transform drugs into more water‑soluble forms, helping them be eliminated more easily. Oral drugs often undergo first‑pass metabolism in the liver, which can significantly reduce their bioavailability before they reach systemic circulation. While the kidneys handle elimination and the lungs metabolize some volatile substances, the liver is by far the primary site for transforming most drugs.