In an IV bolus administration, how does plasma concentration change over time?

In an IV bolus administration, how does plasma concentration change over time?

• A. Starts high and gradually decreases
• B. Starts at zero and rises
• C. Rapidly increases then plateaus
• D. Remains constant

Answer: (A)

In IV bolus administration, there is no absorption phase—the drug is delivered directly into the bloodstream. Right after the injection, the plasma concentration is at its highest (C0, determined by Dose divided by the apparent volume of distribution). Over time, the concentration falls as the drug distributes into tissues and is eliminated by metabolism and excretion. In a simple one-compartment view, this decline is exponential: C(t) = C0 e^{-k t}. So the plasma concentration starts high and gradually decreases. It wouldn’t start at zero and rise, nor stay constant, nor rapidly increase and plateau.

In IV bolus administration, there is no absorption phase—the drug is delivered directly into the bloodstream. Right after the injection, the plasma concentration is at its highest (C0, determined by Dose divided by the apparent volume of distribution). Over time, the concentration falls as the drug distributes into tissues and is eliminated by metabolism and excretion. In a simple one-compartment view, this decline is exponential: C(t) = C0 e^{-k t}. So the plasma concentration starts high and gradually decreases. It wouldn’t start at zero and rise, nor stay constant, nor rapidly increase and plateau.