Which statement best describes the duration of action?

Which statement best describes the duration of action?

• A. True
• B. False; the duration is the time above MEC
• C. False; the duration is the time to reach MEC
• D. False; the duration is the area under the curve

Answer: (B)

Duration of action is determined by how long the drug concentration stays above the minimum effective concentration (MEC). The therapeutic effect only persists as long as the concentration is above MEC; once it drops below MEC, the effect fades. Thus, the correct description is that duration equals the time the drug remains above MEC. The time to reach MEC describes onset, not duration, and the area under the curve reflects overall exposure, not how long the effect lasts.

Duration of action is determined by how long the drug concentration stays above the minimum effective concentration (MEC). The therapeutic effect only persists as long as the concentration is above MEC; once it drops below MEC, the effect fades. Thus, the correct description is that duration equals the time the drug remains above MEC. The time to reach MEC describes onset, not duration, and the area under the curve reflects overall exposure, not how long the effect lasts.