After one half-life, what percentage of the drug remains in the body?

After one half-life, 50% of the drug remains in the body. The concept of half-life is fundamental in pharmacology, referring to the time it takes for the concentration of a drug in the bloodstream to reduce to half of its original value. This reduction occurs due to processes like metabolism and excretion.

Understanding this principle is crucial in pharmacology because it helps clinicians determine dosing schedules and evaluate how long a drug will exert its effects. For example, if a patient takes a medication with a half-life of 4 hours, after 4 hours, 50% of the original dose will still be present in their system. This remaining percentage is critical for understanding the drug's action, efficacy, and safety in treating conditions.

With each subsequent half-life, the remaining drug quantity continues to halve, which is the reason that the remaining percentages of 75%, 87.5%, and 12.5% do not apply after just one half-life.