A drug given intravenously reaches peak concentration in the bloodstream more rapidly than when given subcutaneously.

• A. True
• B. False
• C. Not necessarily
• D. Only in some cases

Answer: (A)

How fast a drug reaches peak concentration depends on how it is given. Intravenous administration places the drug directly into the bloodstream, so it becomes immediately available to circulate. This results in 100% bioavailability and a rapid rise to peak levels, especially if given as a single IV bolus where the peak is essentially instantaneous. Subcutaneous administration requires the drug to be absorbed from the injection site into the bloodstream, a process driven by tissue perfusion and diffusion, which takes time. Therefore, the peak concentration occurs later and is usually lower or more gradual than with IV. If the IV dose is given as an infusion, the peak occurs at the end of the infusion, but still typically sooner than the peak for subcutaneous administration. Overall, IV reaches peak concentration more rapidly than subcutaneous.