Question

A drug with a low clearance and large volume of distribution will have

• A. Long half-life
• B. Low bioavailability
• C. Rapid elimination
• D. Short half-life

Hint:

The elimination half-life of a drug (the time taken for its concentration to fall by half) depends on two things: how much of the body the drug spreads into (volume of distribution, V d ) and how fast the body clears it

Answer 1

The Correct Option is A

Step 1: Recall the half-life formula.
The elimination half-life (t_1/2) of a drug is given by: \( t_{1/2} = \frac{0.693 \times V_d}{CL} \) where V_d is volume of distribution and CL is clearance.

Step 2: Apply the formula to the question.
The question states: low clearance AND large volume of distribution. In the formula, t_1/2 is directly proportional to V_d and inversely proportional to CL. So: large V_d (increases t_1/2) + low CL (also increases t_1/2) = very long half-life.

Step 3: Eliminate the wrong options.
Low bioavailability is about absorption (oral route), unrelated to the clearance-Vd relationship. Rapid elimination and short half-life both mean the opposite of what the formula predicts here.

Step 4: Real-life example.
Drugs like amiodarone (huge V_d, low hepatic clearance) have half-lives of weeks to months. This means the drug stays in the body for a very long time, requiring careful loading and maintenance dosing.

Step 5: Conclusion.
Low clearance with large volume of distribution = prolonged half-life = long-acting drug.


Answer: Option (1) — Long half-life