Due to guidelines that were released earlier this year, you may see a difference in vancomycin monitoring orders for patients who have severe methicillin-resistant Staphylococcus aureus (MRSA) infections. Trough-only monitoring with a target of 15 to 20 mg/L is no longer recommended, based on efficacy and nephrotoxicity data in these patients. To reduce the risk of acute kidney injury (AKI) caused by vancomycin, the new guidelines advocate for monitoring a peak and trough, rather than trough only, in those who have serious MRSA infections, such as:

• Blood stream infections due to central lines
• Pneumonia
• Osteomyelitis
• Sepsis
• Device-related osteoarticular infections (e.g., prosthetic devices)
• Septic Arthritis
• Meningitis
• Brain abscess
• Endocarditis
• Some surgical site infections

In addition, they recommend using specific calculations to determine the amount of vancomycin the patient has actually been exposed to, which is also called area under the curve (AUC). By evaluating AUC and targeting a range of 400 to 600 mg•h/L, we can determine the best dose of vancomycin to treat the infection, while simultaneously reducing the risk for AKI. Your pharmacist will be able to support you or perform calculations upon request.

Some things to consider as this practice begins to emerge are:

• Ensure you know the indication for use for any patients receiving vancomycin
• If the patient was transferred from another facility, ask if they were monitoring AUC, and to give you those results
• Discuss the ongoing monitoring plan with the prescriber at your facility, as most episodes of AKI develop between 4 to 17 days after initiation
• If AUC monitoring is recommended, ensure samples are drawn at the next available peak and trough time after the 3rd or 4th dose
  • Peaks are ideally drawn 1 to 2 hours after the infusion is completed
  • Troughs are drawn at the end of the dosing interval, approximately 30 minutes prior to the next dose

Finally, it is important to remember that regardless of the type of infection, vancomycin can cause kidney injury in high-risk individuals, such as:

• Critically ill patients receiving concurrent nephrotoxins (e.g., aminoglycosides)
• Patients with unstable renal function (i.e., deteriorating or significantly improving)
• Patients receiving prolonged courses of therapy (i.e., over 3 to 5 days)

The frequency of monitoring should be individualized based on the clinical picture of the patient and the judgement of the prescriber. For example, frequent (e.g., twice weekly) or daily monitoring may be prudent for hemodynamically unstable patients (e.g., those with end-stage renal disease), but once weekly monitoring may be acceptable for hemodynamically stable patients.