IV administration provides rapid onset because it bypasses which process?

• A. Infiltration
• B. Pharmacokinetic absorption
• C. First-pass metabolism
• D. Renal clearance

Answer: (B)

When a drug is given by IV, it goes directly into the bloodstream, so there’s no barrier to crossing the bodily membranes for absorption. Absorption is the process by which a drug moves from its site of administration into the circulatory system. Because this step is skipped with IV administration, the drug is immediately available in the blood, leading to a rapid onset of action.

It’s also true that intravenous delivery bypasses first-pass metabolism, which can increase the amount of drug reaching systemic circulation for some medications, but the speed of onset is best explained by bypassing the absorption step. Other processes, like infiltration or renal clearance, relate to tissue leakage or elimination, respectively, and do not account for why the onset is rapid.