Drug Absorption · Pharmacology

What is the primary reason that insulin is administered parenterally (injection) rather than orally?

  1. It is too lipid-soluble to be absorbed
  2. It causes severe gastric ulcers if swallowed
  3. It has a very high molecular weight that prevents any diffusion
  4. It is a protein that would be degraded by digestive enzymes and gastric acid
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Correct answer: It is a protein that would be degraded by digestive enzymes and gastric acid

Insulin is a polypeptide; if taken orally, proteases in the stomach and small intestine would break it down into amino acids. This would render the hormone inactive before it could ever be absorbed into the bloodstream.

Difficulty: Medium Question 11 of 20

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