Where will weak acids be ion trapped?

Where will weak acids be ion trapped?

• A. Small intestines
• B. Stomach
• C. Large intestine
• D. Blood

Answer: (A)

Ion trapping works because ionized forms cross membranes poorly, so a drug that is a weak acid will become ionized in a more basic environment and get stuck there. The small intestine has a higher (more basic) pH than the stomach. A weak acid that moves into the intestinal lumen is exposed to this higher pH, becomes ionized, and cannot easily cross back across the intestinal wall. That makes it trapped in the intestinal compartment. In contrast, the stomach is very acidic, so the weak acid stays largely non-ionized and can cross membranes more readily, so it’s not trapped there. The other options don’t provide the same clear basic environment relative to the stomach as the small intestine does.

Ion trapping works because ionized forms cross membranes poorly, so a drug that is a weak acid will become ionized in a more basic environment and get stuck there.

The small intestine has a higher (more basic) pH than the stomach. A weak acid that moves into the intestinal lumen is exposed to this higher pH, becomes ionized, and cannot easily cross back across the intestinal wall. That makes it trapped in the intestinal compartment.

In contrast, the stomach is very acidic, so the weak acid stays largely non-ionized and can cross membranes more readily, so it’s not trapped there. The other options don’t provide the same clear basic environment relative to the stomach as the small intestine does.