ABC, a new, weakly acidic drug, is being tested and formulated for oral administration. Previous testing of showed that if ABC is dissolved in a solution of pH 7.4 (blood pH) the equilibrium concentration of unionized drug is 0.001 M and the concentration of ionized drug is 0.1 M.
The experimental setup consists of two chambers separated by an excised piece of digestive endothelium. The environment in either chamber can be controlled, and only unionized drug passes through the membrane.
Two experiments are performed with equal amounts of drug placed in chamber I:
- stomach endothelium is used as a membrane and pH of chamber I is set to 3.4.
- intestinal membrane is used, and the pH of I is adjusted to 6.4.
Assuming no amount of drug is lost from the chamber and based on pH-partition theory, which experiment A or B should allow for better absorption of drug?
Experiment B resulted in higher drug levels in chamber II (vessel lumen). Does this agree with the equilibrium results? Explain why or why not.