What is the primary reason that drug precipitation in the stomach reduces absorption?

What is the primary reason that drug precipitation in the stomach reduces absorption?

• A. It increases drug solubility
• B. It prevents dissolution and passage to absorption sites
• C. It accelerates gastric emptying
• D. It enhances permeability of mucosa

Answer: (B)

The key idea is that absorption of an oral drug depends on how much of it is dissolved in GI fluids. Only the dissolved form can diffuse across the intestinal lining into the bloodstream, and for many drugs, dissolution is the rate‑limiting step before absorption. When a drug precipitates in the stomach, it shifts from dissolved to solid form, reducing the amount present in solution that can reach the intestinal absorption surface. With less dissolved drug available, the driving force for diffusion into the mucosa drops, so overall absorption decreases and bioavailability falls. Precipitation essentially removes the drug from the pool that can be absorbed. The other options don’t fit this mechanism: increasing solubility would help absorption; preventing dissolution would obviously hinder absorption but precipitation is the process causing non‑dissolution; accelerating gastric emptying or increasing mucosal permeability would not explain a drop in absorption when precipitation occurs.

The key idea is that absorption of an oral drug depends on how much of it is dissolved in GI fluids. Only the dissolved form can diffuse across the intestinal lining into the bloodstream, and for many drugs, dissolution is the rate‑limiting step before absorption.

When a drug precipitates in the stomach, it shifts from dissolved to solid form, reducing the amount present in solution that can reach the intestinal absorption surface. With less dissolved drug available, the driving force for diffusion into the mucosa drops, so overall absorption decreases and bioavailability falls. Precipitation essentially removes the drug from the pool that can be absorbed.

The other options don’t fit this mechanism: increasing solubility would help absorption; preventing dissolution would obviously hinder absorption but precipitation is the process causing non‑dissolution; accelerating gastric emptying or increasing mucosal permeability would not explain a drop in absorption when precipitation occurs.