What should be done for a patient with a Vancomycin trough level of 18 mg/L?

Management of Vancomycin Trough Level of 18 mg/L

A vancomycin trough level of 18 mg/L is within the therapeutic range (15-20 mg/L) for serious infections and does not require dose adjustment, but continued monitoring of renal function is essential. 1

Interpretation of Trough Level

• A trough level of 18 mg/L falls within the target range of 15-20 mg/L recommended for serious infections by the Infectious Diseases Society of America and the American Society of Health-System Pharmacists 1
• This level indicates adequate therapeutic coverage while remaining below levels associated with increased toxicity risk
• The current dosing regimen appears appropriate based on this trough level

Recommended Actions

1. Continue current dosing regimen if treating a serious infection such as:

   • Staphylococcal septicemia
   • Osteomyelitis
   • Brain abscess/CNS infections
   • Endocarditis

2. Monitor renal function by checking serum creatinine at least twice weekly

   • Critical step as vancomycin at trough levels of 15-20 mg/L carries increased nephrotoxicity risk 1
   • Watch for multiple consecutive increases in serum creatinine (increase of 0.5 mg/dL or 150% from baseline)

3. Continue trough level monitoring:

   • Check levels twice weekly for patients on extended therapy
   • Ensure proper timing of trough collection (immediately before next scheduled dose)
   • Improperly timed samples can lead to falsely elevated readings and inappropriate dose reductions 2

Important Considerations

• The most appropriate vancomycin therapeutic target is an AUC of 400-600 mg*hr/L, with AUC/MIC being the best predictor of efficacy 1
• While trough monitoring is still common practice, recent guidelines advocate for AUC/MIC monitoring using Bayesian calculations 3
• If the patient shows signs of nephrotoxicity, consider:
  • More frequent monitoring of renal function
  • Evaluating for concomitant nephrotoxic medications
  • Potentially adjusting the dose if renal function deteriorates

Pitfalls to Avoid

1. Improper timing of trough levels:

   • Drawing levels too early can lead to falsely elevated readings (41.3% of specimens in one study) 2
   • This can result in inappropriate dose reductions and potential underdosing

2. Focusing only on trough levels:

   • While a trough of 18 mg/L is within target range, consider the clinical response
   • If infection is not improving despite appropriate trough levels, reevaluate diagnosis or consider alternative antibiotics

3. Neglecting renal function monitoring:

   • Even with therapeutic trough levels, nephrotoxicity remains a concern
   • Regular monitoring of serum creatinine is essential

4. Inappropriate duration of therapy:

   • Ensure appropriate treatment duration based on infection type:
     • Staphylococcal septicemia: 7-14 days
     • Osteomyelitis: at least 6-8 weeks
     • Brain abscess/CNS infections: at least 4-6 weeks
     • Endocarditis: at least 6 weeks 1