Question

If the amount of drug in the body declines from 100% of the dose (IV bolus injection) to 15% of the dose in 24 hours (zero-order), what percentage of the dose remains after 48 hours?

Answer 1

The remaining percentage of the drug after 48 hours can be calculated using the formula for zero-order kinetics. After three half-lives, the drug percentage remaining is 3.75%.

Step-by-step explanation:

To calculate the percentage of the drug remaining after 48 hours, we need to determine the number of half-lives that have passed. Since the drug follows zero-order kinetics, meaning a constant amount is eliminated per unit time, we can use the formula:

Remaining Percentage = (Initial Percentage) x (1 - 0.5)(time in hours / half-life in hours)

Given that the amount declines from 100% to 15% in 24 hours, we can calculate the half-life using the equation:

(Initial Percentage) = (Final Percentage) x (0.5)(time in hours / half-life in hours)

Solving this equation gives us a half-life of 16 hours. Thus, after 48 hours, three half-lives have passed:

Remaining Percentage = 15% x (1 - 0.5)(48 / 16) = 3.75%