To increase absorption when equilibrium at the absorption site is reached, which strategy is effective?

To increase absorption when equilibrium at the absorption site is reached, which strategy is effective?

• A. Increase blood flow to establish a stronger concentration gradient so drug molecules move into blood/lymph
• B. Decrease blood flow to maintain equilibrium
• C. Increase the drug's molecular weight to slow diffusion
• D. Reduce the absorption surface area to minimize uptake

Answer: (A)

The driving force for absorption is the concentration gradient across the absorption barrier. When equilibrium is reached, there’s no net transfer because the concentrations on both sides are the same. To increase absorption after equilibrium, you need to renew or maintain that gradient. Increasing blood flow does exactly that: it removes the drug from the blood side more quickly, keeping its concentration lower there and sustaining a difference across the barrier, which drives more drug into the bloodstream or lymph. The other options don’t help in this context. Slowing diffusion by increasing molecular weight makes crossing the barrier harder. Reducing the absorbing surface area decreases contact with the barrier, lowering uptake. Decreasing blood flow would allow the drug to accumulate near the site and reduce the gradient, further hindering absorption.

The driving force for absorption is the concentration gradient across the absorption barrier. When equilibrium is reached, there’s no net transfer because the concentrations on both sides are the same. To increase absorption after equilibrium, you need to renew or maintain that gradient. Increasing blood flow does exactly that: it removes the drug from the blood side more quickly, keeping its concentration lower there and sustaining a difference across the barrier, which drives more drug into the bloodstream or lymph.

The other options don’t help in this context. Slowing diffusion by increasing molecular weight makes crossing the barrier harder. Reducing the absorbing surface area decreases contact with the barrier, lowering uptake. Decreasing blood flow would allow the drug to accumulate near the site and reduce the gradient, further hindering absorption.