When to draw vancomycin (Vancomycin hydrochloride) trough levels?

From the Guidelines

Vancomycin levels should be drawn just before the fourth dose when administering the standard dosing regimen, as this timing ensures the measurement captures the lowest concentration of the drug in the bloodstream before the next dose is given. This approach is supported by the Infectious Diseases Society of America guidelines, which recommend obtaining trough serum vancomycin concentrations at steady state conditions, prior to the fourth or fifth dose 1. The target trough level typically ranges from 10-20 mg/L, with higher targets (15-20 mg/L) for more serious infections like endocarditis, osteomyelitis, meningitis, or pneumonia, as these levels are associated with improved clinical response and microbiologic eradication 1.

Key Considerations

• Trough vancomycin concentrations are the most accurate and practical method to guide vancomycin dosing 1
• Monitoring of peak vancomycin concentrations is not recommended 1
• Vancomycin trough concentrations of 15–20 mg/L are recommended for serious infections, such as bacteremia, infective endocarditis, osteomyelitis, meningitis, pneumonia, and severe SSTI due to MRSA 1
• Trough vancomycin monitoring is recommended for serious infections and patients who are morbidly obese, have renal dysfunction, or have fluctuating volumes of distribution 1

Clinical Application

• For patients on alternative dosing schedules, the sample should still be collected 30 minutes before the fourth dose, regardless of the interval
• Once steady state is achieved and if the dose remains unchanged, subsequent levels can be monitored weekly unless the patient's renal function changes significantly, which would warrant more frequent monitoring
• Vancomycin doses of 15–20 mg/kg/day every 8–12 h are recommended for adult patients on the basis of actual body weight and are adjusted for the patient’s estimated creatinine clearance, not to exceed 2 g per dose 1

From the FDA Drug Label

In subjects with normal kidney function, multiple intravenous dosing of 1 g of vancomycin (15 mg/kg) infused over 60 minutes produces mean plasma concentrations of approximately 63 mcg/mL immediately after the completion of infusion, mean plasma concentrations of approximately 23 mcg/mL 2 hours after infusion, and mean plasma concentrations of approximately 8 mcg/mL 11 hours after the end of the infusion.

The FDA drug label does not answer the question.

From the Research

Vancomycin Trough Levels

• The timing of drawing vancomycin trough levels is crucial for monitoring its effectiveness and minimizing the risk of nephrotoxicity 2.
• According to a study, serum trough vancomycin concentrations should be drawn within 15 to 45 minutes before the fourth vancomycin dose 2.
• Another study suggests that measuring trough vancomycin concentrations during intermittent dosing can be used as a surrogate for the area under the concentration-time curve (AUC24) 3.
• However, it is noted that trough concentrations are a misleading surrogate for AUC24 and a poor endpoint in themselves, and alternative methods such as log-linear pharmacokinetic methods or Bayesian methods may be superior 3.

Factors Influencing Vancomycin Trough Levels

• Several factors can influence vancomycin trough levels, including age, gender, site of infection, and type of admission 2.
• A study found that females, patients older than 50 years, and those admitted to the coronary care unit (CCU) or cardiac surgery intensive care unit (CSICU) had significantly higher trough levels of vancomycin 2.
• Another study found that scheduled vancomycin dosing regimens can help achieve target trough levels, and that dosing strategies should be based on ultrafiltration rate and patient-specific factors 4.

Monitoring and Dosing Strategies

• Regular monitoring of vancomycin trough levels is essential to ensure that the drug is being used effectively and safely 5.
• A study found that only 15.7% of measured troughs were within the target therapeutic level, highlighting the need for improved monitoring and dosing practices 5.
• Alternative dosing strategies, such as continuous infusion, may also be effective in achieving target trough levels and reducing the risk of nephrotoxicity 3.