Question

First pass metabolism occurs mainly in _______

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

Hint:

First pass metabolism mainly occurs in the liver and can reduce the bioavailability of orally administered drugs.

Answer 1

The Correct Option is B

The question asks about the primary site of first-pass metabolism. Let's analyze the key concepts involved to determine the correct answer.

Understanding First-Pass Metabolism:

First-pass metabolism, also known as first-pass effect or presystemic metabolism, refers to the initial metabolism of a drug's active molecules within the body before it reaches systemic circulation. This process predominantly affects oral medications. The drug undergoes a significant transformation during absorption, often reducing the concentration of active pharmaceutical ingredients in the bloodstream.

Explanation of Options:

• Kidney: The kidneys primarily function in the excretion and filtration of blood and do not significantly contribute to first-pass metabolism.
• Liver: The liver is the primary organ responsible for first-pass metabolism. It contains enzymes that significantly transform nutrients and drugs absorbed from the gastrointestinal tract.
• Lungs: The lungs mainly facilitate gaseous exchange and are not involved in drug metabolism immediately after absorption.
• Skin: The skin acts as a protective barrier and is not a site for first-pass metabolism.

Conclusion:

Based on the explanation above, the liver is primarily responsible for first-pass metabolism. The liver's enzymes (such as the cytochrome P450 family) play a crucial role in this process.

Therefore, the correct answer is: Liver.