A basic drug has a pKa of 9. Would it be more easily absorbed in a pH environmen
ID: 145751 • Letter: A
Question
A basic drug has a pKa of 9. Would it be more easily absorbed in a pH environment of 12 or 6?
It will be more easily absorbed in the pH 12 environment because the drug will be more ionized in that environment.
It will be more easily absorbed in the pH 6 environment because the drug will be more ionized in that environment.
It will be more easily absorbed in the pH 6 environment because the drug will be less ionized in that environment.
It will be more easily absorbed in the pH 12 environment because the drug will be less ionized in that environment.
It will be equally absorbed in both environments because the difference in pH and pKa is the same for both pH 12 and pH 6 environment.
A.It will be more easily absorbed in the pH 12 environment because the drug will be more ionized in that environment.
B.It will be more easily absorbed in the pH 6 environment because the drug will be more ionized in that environment.
C.It will be more easily absorbed in the pH 6 environment because the drug will be less ionized in that environment.
D.It will be more easily absorbed in the pH 12 environment because the drug will be less ionized in that environment.
E.It will be equally absorbed in both environments because the difference in pH and pKa is the same for both pH 12 and pH 6 environment.
Explanation / Answer
The membranes that a drug has to cross are made of phospholipids and allow the easier transport of unionized, non-polar molecules. (Option A and B are incorrect)
A basic drug will be ionized in an acidic environment. Hence, it will not be well absorbed there.
Basic drugs are absorbed in the small intestine which has a pH of 7.4.
The drug will be less ionized in an environment of pH 12 as compared to pH 6 since pH 6 is acidic and pH 12 is basic. (option C is incorrect).
Option E is very misleading. pKa is the pH at which the drug is 50% ionized. The difference in pKa and pH on either side of the scale will yield very different results.
Option D is correct. The drug is least ionized at pH 12 and will get absorbed easily.
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