Peak drug levels are used to determine:

• A. Adequacy of drug activity
• B. Interval of the drug administration
• C. Maximum drug concentration
• D. Therapeutic range

Answer: (C)

Peak drug levels show the highest amount of medication in the bloodstream after a dose, so they are used to determine the maximum drug concentration (Cmax) a patient experiences. Knowing this helps prevent toxicity by ensuring the dose doesn’t push concentrations above the safe upper limit. Therapeutic drug monitoring uses peak levels to guard the upper end of the therapeutic window, while trough levels help confirm the minimum concentration is maintained.