I.Asprin is a weak acid (pKa-3.5) that is taken up into the bloodstream by diffu

Question

I.Asprin is a weak acid (pKa-3.5) that is taken up into the bloodstream by diffusion through cells lining the stomach and small intestine. Aspirin crosses the plasma membrane of a cell most effectively in its uncharged form; in its charged form it cannot cross the hydrophobic lipid bilayer of the membrane. The pH of the stomach is about 1.5, and that of the lumen of the small intestine is about 6.0. Is the majority of the aspirin absorbed in the stomach or in the intestine? Explain your reasoning in light of the chemical structure of aspirin.

Explanation / Answer

The basic principle is that drugs are absorbed more in their ionoc form.

For aspirin , it is an acidic drug (salicylic acid) it ionose at a basic pH than acidic. So it doesn't dissociate inti ions on stomach but after reaching intestine it dissociates. And hence absorbed more in intestine.

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