What is the consequence of a displacement interaction at plasma proteins?

What is the consequence of a displacement interaction at plasma proteins?

• A. Decreased unbound fraction
• B. Increased unbound fraction, potentially altering distribution, clearance, or toxicity
• C. No effect on distribution
• D. Decreased tissue uptake

Answer: (B)

Displacement at plasma proteins occurs when another drug competes for binding sites on albumin or other carrier proteins, pushing the bound drug into the unbound, active form. Only the unbound drug can cross membranes, diffuse into tissues, be metabolized, and be excreted, so the displaced drug shows a higher unbound fraction. This increases the amount that distributes into tissues (distribution), provides more substrate for clearance processes (clearance), and raises the risk of adverse effects or toxicity due to higher free drug concentrations. The total plasma level may not change immediately because the bound pool can re-equilibrate, but the free concentration rises and can lead to significant pharmacodynamic and pharmacokinetic consequences.

Displacement at plasma proteins occurs when another drug competes for binding sites on albumin or other carrier proteins, pushing the bound drug into the unbound, active form. Only the unbound drug can cross membranes, diffuse into tissues, be metabolized, and be excreted, so the displaced drug shows a higher unbound fraction. This increases the amount that distributes into tissues (distribution), provides more substrate for clearance processes (clearance), and raises the risk of adverse effects or toxicity due to higher free drug concentrations. The total plasma level may not change immediately because the bound pool can re-equilibrate, but the free concentration rises and can lead to significant pharmacodynamic and pharmacokinetic consequences.