Why are trough levels used for vancomycin, and what is a typical target range (in mcg/mL) depending on infection?

• A. To measure peak concentration
• B. To evaluate hydration status
• C. To adjust dosing based on liver function
• D. To balance efficacy and toxicity by ensuring trough levels within a target range

Answer: (D)

Monitoring trough levels for vancomycin is about balancing how much drug exposure the patient has with the goal of killing the infection while minimizing kidney toxicity. The trough is the lowest concentration right before the next dose, so adjusting the dose or dosing interval based on that value helps keep drug levels within a safe and effective range.

Typical targets depend on how serious the infection is. For less severe infections, a trough around 10–15 mcg/mL is often adequate. For more serious or invasive infections (such as bacteremia, pneumonia, meningitis, endocarditis, or osteomyelitis), the target trough is typically higher, around 15–20 mcg/mL. Keep in mind that newer guidelines emphasize estimating overall exposure with AUC/MIC rather than troughs alone, but trough monitoring remains a common practical approach.