For vancomycin used to treat meningitis, when should the peak level be drawn relative to the end of the dose infusion?

• A. At the completion of the infusion
• B. 30 minutes after the end of the infusion
• C. 60 minutes after the end of the infusion
• D. 60 minutes after the infusion has begun

Answer: (C)

Timing of vancomycin peak sampling hinges on allowing distribution to complete so the measured Cmax reflects the true peak. If you draw at the end of the infusion or during the infusion, the level is still rising and has not reached its distributional peak, leading to an inaccurately high or unstable value. Waiting about one hour after the infusion finishes lets the drug distribute into tissues and reach its true maximum in the serum, giving a reliable peak measurement. This timing is used even when treating meningitis, to ensure the measured peak accurately reflects exposure without being confounded by ongoing infusion.