True or False: If a small drug particle reaches the alveoli and is digested by resident macrophages, the overall concentration of drug absorbed will be lower.

True or False: If a small drug particle reaches the alveoli and is digested by resident macrophages, the overall concentration of drug absorbed will be lower.

• A. True
• B. Not determinable
• C. It depends on particle charge
• D. False

Answer: (D)

Inhaled drug absorption depends on how fast the drug dissolves in the lung lining fluid and how readily it crosses the alveolar epithelium into the blood. Alveolar macrophages do phagocytose particles and can digest them, but this does not automatically mean less drug will be absorbed. The drug molecules released during or after macrophage processing can diffuse into the lining fluid and then be taken up into the bloodstream, or be trafficked via lymphatics, leading to ongoing or even substantial systemic exposure. Additionally, some drugs may be designed to withstand or be released slowly from macrophages, prolonging absorption rather than reducing it. So the fact that a particle is digested by alveolar macrophages does not universally produce a lower overall absorbed concentration.

Inhaled drug absorption depends on how fast the drug dissolves in the lung lining fluid and how readily it crosses the alveolar epithelium into the blood. Alveolar macrophages do phagocytose particles and can digest them, but this does not automatically mean less drug will be absorbed. The drug molecules released during or after macrophage processing can diffuse into the lining fluid and then be taken up into the bloodstream, or be trafficked via lymphatics, leading to ongoing or even substantial systemic exposure. Additionally, some drugs may be designed to withstand or be released slowly from macrophages, prolonging absorption rather than reducing it. So the fact that a particle is digested by alveolar macrophages does not universally produce a lower overall absorbed concentration.