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

The correct answer is: a. One hour after completion of the IV dose and one hour before the next administration of the medication.

Explanation:

Choice A Rationale: Drawing blood one hour after completion of the IV dose and one hour before the next administration of the medication is the optimal timing for obtaining peak and trough levels of vancomycin. The peak level represents the highest concentration of the drug in the bloodstream, typically occurring shortly after the completion of the infusion. By drawing blood one hour post-infusion, healthcare providers can capture the peak concentration accurately. Similarly, drawing blood one hour before the next dose allows for the determination of the trough level, representing the lowest concentration of the drug in the bloodstream just before the subsequent dose is administered. These time points provide a comprehensive assessment of vancomycin serum levels, aiding in therapeutic monitoring and dose adjustment to optimize efficacy while minimizing the risk of toxicity.

Choice B Rationale: Drawing blood two hours after completion of the IV dose and two hours before the next administration may not accurately capture the peak and trough levels of vancomycin. The timing intervals are too distant from the dosing intervals, potentially leading to inaccurate assessments of drug concentrations. Waiting two hours post-infusion may result in missing the peak concentration, while drawing blood two hours pre-administration may not reflect the true trough level, as the drug may have already begun to accumulate in the bloodstream in anticipation of the next dose. Suboptimal timing could compromise the precision of therapeutic monitoring and decision-making regarding dosage adjustments.

Choice C Rationale: Drawing blood 30 minutes into the administration and 30 minutes before the next administration does not provide sufficient time for vancomycin to reach its peak and trough levels in the bloodstream. Peak levels typically occur shortly after the completion of the infusion, while trough levels reflect the drug's lowest concentration just before the next dose. Thirty minutes into the infusion may not accurately represent the peak concentration, as the drug may still be reaching its maximum levels in the bloodstream. Similarly, drawing blood 30 minutes pre-administration may not capture the true trough level, as the drug may not have fully depleted from the bloodstream at this early time point.

Choice D Rationale: Drawing blood immediately after completion of the IV dose does not allow sufficient time for vancomycin to reach its peak concentration in the bloodstream. Peak levels typically occur shortly after the infusion is completed, as the drug rapidly enters the systemic circulation. Drawing blood immediately post-infusion may lead to underestimation of the peak concentration, as it takes time for the drug to distribute and equilibrate within the body's compartments. Additionally, drawing blood only 30 minutes before the next administration may not accurately reflect the trough level, as the drug may not have reached its lowest concentration in the bloodstream. Waiting until one hour before the next dose allows for a more reliable assessment of the trough level, ensuring accurate therapeutic monitoring and dosage adjustments.