What percentage of a drug remains in the body after two half-lives?

To determine what percentage of a drug remains in the body after two half-lives, it’s essential to understand the concept of a drug's half-life. The half-life of a drug is the time it takes for the concentration of the drug in the bloodstream to reduce to half its initial value.

After the first half-life, 50% of the drug remains in the body. When another half-life passes (the second half-life), the remaining quantity of the drug is halved again. Thus, from the 50% that was remaining after the first half-life, an additional half (which is 25%) will be eliminated.

This means that after the two half-lives, only 25% of the drug remains in the body. Consequently, this also implies that 75% of the drug has been cleared from the system.

This reasoning confirms that the correct interpretation of the data leads to the conclusion that after two half-lives, 25% of the drug remains. Hence, the percentage of clearance is 75%. This understanding of pharmacokinetics is crucial for patients' medication management, illustrating how drug levels decrease over time and informing appropriate dosing intervals.