Some drugs like MDMA (Ecstasy, pKa 9.9) are so basic that they do not exist in any appreciable quantities in the neutral B form in the digestive tract. Yet, they are still absorbed. What factors allow for this?

Question

Quizplus · Accepted Answer

All three options listed (A, B, and C) can contribute to the absorption of highly basic drugs like MDMA, as they help to facilitate passage across the lipid bilayer of cell membranes in the digestive tract. Option A highlights the large surface area of the GI tract that can potentially serve as a site of absorption. Option B points out that any basic (charged) molecules that do exist will be rapidly deprotonated (stripped of their positive charge) upon passing through the highly acidic environment of the stomach, allowing for better passage across the membrane. Finally, option C alludes to the fact that the movement of liquid phases (such as bile) on both sides of the lipid bilayer can help to dissolve the drug and facilitate its transport through the membrane. Together, the three factors listed in options A, B, and C can contribute to the efficient absorption of highly basic drugs like MDMA, despite the fact that they may not exist in appreciable quantities in their charged (B) form.

Some Drugs Like MDMA (Ecstasy, PKa 9