A client is receiving intravenous (IV) vancomycin and the nurse plans to draw blood for a peak and trough to determine the serum level of the drug. Which collection times provide the best determination of these levels?

choice A, Drawing the peak level two hours after the IV dose is too late to capture the drug's highest serum concentration. Similarly, drawing the trough two hours before the next dose does not reflect the lowest drug level accurately. Choice B, Drawing the peak level one hour after completion of the IV dose ensures an accurate measurement of the highest serum concentration, as vancomycin typically peaks within this time frame. Drawing the trough one hour before the next dose ensures the lowest concentration of the drug is measured, providing precise therapeutic monitoring. Choice C is incorrect because drawing blood 30 minutes into the IV dose would not allow the full dose to circulate and reach peak levels in the bloodstream. Choice D. Drawing the peak level immediately after the completion of the IV dose is too early, as the drug needs time to distribute in the bloodstream and reach its highest concentration. While drawing the trough 30 minutes before the next dose is appropriate, the incorrect timing of the peak makes this option unsuitable.