Question

In one-compartment model, after IV bolus administration, the plasma concentration declines

• A. Sigmoidally with time
• B. Exponentially with time
• C. Logarithmically with time
• D. Linearly with time

Hint:

In a one-compartment model, the body is treated as a single uniform space. When a drug is given as an IV bolus (the whole dose injected at once into the blood), it spreads instantly and then starts to be eliminated.

Answer 1

The Correct Option is B

Concept:
In a one-compartment model, the body is treated as a single uniform space. When a drug is given as an IV bolus (the whole dose injected at once into the blood), it spreads instantly and then starts to be eliminated. The way the plasma concentration falls over time depends on the order of elimination.

Step 1: Most drugs follow first-order elimination, meaning a constant fraction is removed per unit time. Mathematically this gives \( C = C_0 \, e^{-kt} \), which is an exponential decline.

Step 2: So on a normal (linear) graph, the plasma concentration curves downward exponentially. (If you plot the log of concentration versus time, it becomes a straight line — but the actual concentration itself declines exponentially.)

Answer: Option (2) — In a one-compartment model after IV bolus, the plasma concentration declines Exponentially with time. (2)