**Question:** Elimination after 3 half lives in first order kinetics is:

**Core Concept:** First order kinetics refers to a model in pharmacokinetics where the rate of drug elimination is proportional to the concentration of the drug in the body. In this context, "half-lives" refers to the time it takes for the concentration of a drug to decrease by half due to elimination.

**Why the Correct Answer is Right:** If the elimination follows first order kinetics, the elimination half-life (t1/2) can be calculated using the formula: t1/2 = ln(2) / k, where 'k' is the elimination rate constant. In this scenario, the elimination occurs over 3 half-lives. Therefore, the concentration of the drug will decrease by half every time, and the drug will be eliminated from the body after 3 complete cycles of half-life.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because the correct answer is based on the concept of elimination over 3 half-lives in first order kinetics.
B. This option is incorrect because the correct answer is based on the concept of elimination over 3 half-lives in first order kinetics.
C. This option is incorrect because the correct answer is based on the concept of elimination over 3 half-lives in first order kinetics.
D. This option is incorrect because the correct answer is based on the concept of elimination over 3 half-lives in first order kinetics.

**Clinical Pearl:** Understanding first order kinetics and elimination half-lives is essential for predicting drug concentrations and adjusting dosages in clinical practice. A drug with a half-life of 6 hours will take 12 hours (6 x 2) to decrease to one-fourth of its initial concentration, and 24 hours (6 x 4) to decrease to one-eighth. This helps pharmacologists and physicians in determining appropriate dosages for optimal therapeutic effects and minimizing side effects.