Low Correlation Between Vancomycin Area Under the Curve Over 24 Hours to the MIC (AUC/MIC ratio) and the Trough Concentration at Steady State in Methicillin-Resistant Staphylococcus Aureus Pneumonia

Abstract

Background : Vancomycin is a mainstay of treatment of serious methicillin-resistant Staphylococcus aureus (MRSA) infections. The recently published guideline on vancomycin monitoring recommends that a vancomycin loading dose can be considered and an individualized target AUC/MIC ratio of 400-600 and should be advocated to achieve clinical efficacy while improving safety in patients with the suspected or definitive MRSA infections.

Methods : To evaluate the correlation between the vancomycin trough concentration and the area under the curve over 24 hours to the MIC (AUC/MIC) ratio according to the guideline recently published. A retrospective cohort study was conducted on adult patients treated for MRSA proven pneumonia with the vancomycin. We enrolled patients administered with the vancomycin loading dose before the maintenance dose and the monitored vancomycin trough concentrations at the steady state in medical intensive care units April 2017-March 2020. We calculated the vancomycin AUC/MIC ratio based on the trough concentration measured for each patient using the Bayesian software. The difference between the microbiological cure, all-cause mortality, and nephrotoxicity for each group was studied.

Results : There was low correlation between the vancomycin AUC/MIC and trough concentration in MRSA pneumonia. A total of 35 patients were included. Thirty-one patients (88.6%) were above the AUC/MIC ratio 400, while 19 patients (54.3%) were in the trough range above 15 mcg/ ml. Although there was a weak correlation between the vancomycin trough concentration and the AUC/MIC ratio (r=0.427, p=0.010), the vancomycin through concentrations at the steady state within the therapeutic ranges did not mean the vancomycin AUC/MIC ratio within the therapeutic ranges (p=0.580). No significant difference was observed in the microbiological cure, all-cause mortality, and incidence of acute kidney injury in each group.

Conclusion : The trough level-guided monitoring of the vancomycin should be replaced by the AUC/MIC ratio-guided monitoring in the clinical practice in Korea.