A weakly basic drug with a pKa of 7.5 partitions from the blood into OF with a pH of 6.7. If ion trapping occurs, where will the drug be trapped?

Question

Quizplus · Accepted Answer

The drug with a pKa of 7.5 exists primarily in its unionized form in blood at physiological pH (neutral to slightly acidic). When it partitions into OF with a lower pH of 6.7, it will become more ionized and therefore trapped in its ionized form. Since OF has a lower pH than blood, the drug will likely be trapped in the more ionized form in the oral fluid. Therefore, choice B is correct.

A Weakly Basic Drug with a PKa of 7