Question

The best explanation for the absorption of salicylic acid from intestine, despite being ionized is:

• A. High surface area of the drug molecules
• B. Dissolution of drug
• C. Availability of 1% of the un-ionized form
• D. Availability of receptors

Hint:

Drug absorption depends on lipid solubility of the un-ionized form — even 1\% can be enough if the surface area is high.

Answer 1

The Correct Option is C

Only the un-ionized form of a weak acid like salicylic acid is absorbed effectively across the lipid membrane. Even though the majority is ionized in the intestine, a small fraction (1%) remains un-ionized and allows for absorption.