If a drug is absorbed into the blood but is inactivated before reaching the site of action, which statement best describes this scenario?

• A. High Absorption at Site of Administration but Low at Site of Action
• B. High Absorption at Site of Action but Low at Site of Administration
• C. No Absorption at Either Site
• D. High Absorption at Both Sites

Answer: (A)

The main point is that a drug’s therapeutic effect depends on how much active drug actually reaches the site of action. If the drug is well absorbed into the blood but is inactivated before it can reach its target, the amount that arrives at the site of action in active form is small. So you can have high absorption from the administration site (the drug gets into the bloodstream readily) but low exposure at the site where it needs to act because it’s being inactivated during transit. That’s why the statement describing high absorption at the administration site but low amount at the site of action best fits this scenario.