Answer :
Final answer:
The pH of the stomach is the critical factor influencing drug absorption in the gastrointestinal tract.
Explanation:
pH - This is the correct answer.
The most important factor that determines absorption within the stomach is pH. Weak organic acids, which exist in a diffusible, nonionized and lipid-soluble form are readily absorbed in the high acidity of the stomach (pH 1-3). In contrast, weak bases will be highly ionized and therefore poorly absorbed.
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