title: Underestimation of the calculated area under the concentration-time curve based on serum creatinine for vancomycin dosing.
abstract: BACKGROUND
  The ratio of the steady-state 24-hour area under the concentration-time curve (ssAUC24) to the MIC (AUC24/MIC) for vancomycin has been recommended as the preferred pharmacodynamic index. The aim of this study was to assess whether the calculated AUC24 (cAUC24) using the creatinine clearance (CLcr) differs from the ssAUC24 based on the individual pharmacokinetic data estimated by a commercial software.
  
  
  METHODS
  The cAUC24 was compared with the ssAUC24 with respect to age, body mass index, and trough concentration of vancomycin and the results were expressed as median and interquartile ranges. A correlation between the cAUC24 and ssAUC24 and the trough concentration of vancomycin was evaluated. The probability of reaching an AUC24/MIC of 400 or higher was compared between the cAUC24 and ssAUC24 for different MICs of vancomycin and different daily doses by simulation in a subgroup with a trough concentration of 10 mg/L and higher.
  
  
  RESULTS
  The cAUC24 was significantly lower than the ssAUC24 (392.38 vs. 418.32 mg·hr/L, P < 0.0001) and correlated weakly with the trough concentration (r = 0.649 vs. r = 0.964). Assuming a MIC of 1.0 mg/L, the probability of reaching the value of 400 or higher was 77.5% for the cAUC24/MIC and 100% for the ssAUC24/MIC in patients with a trough concentration of 10 mg/L and higher. If the MIC increased to 2.0 mg/L, the probability was 57.7% for the cAUC24/MIC and 71.8% for the ssAUC24/MIC at a daily vancomycin dose of 4,000 mg.
  
  
  CONCLUSIONS
  The cAUC24 using the calculated CLcr is usually underestimated compared with the ssAUC24 based on individual pharmacokinetic data. Therefore, to obtain a more accurate AUC24, therapeutic monitoring of vancomycin rather than a simple calculation based on the CLcr should be performed, and a more accurate biomarker for renal function is needed.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Sung Joon
authors.initials: SJ
authors.lastname: Jin
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Yoon
authors.affiliation: Therapeutic Drug Monitoring Team, Gangnam Severance Hospital, Seoul, Korea.
authors.forename: Bo Sook
authors.initials: BS
authors.lastname: Ahn
authors.affiliation: Therapeutic Drug Monitoring Team, Gangnam Severance Hospital, Seoul, Korea.
authors.forename: Ji Ah
authors.initials: JA
authors.lastname: Chung
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea. ; Therapeutic Drug Monitoring Team, Gangnam Severance Hospital, Seoul, Korea.
authors.forename: Young Goo
authors.initials: YG
authors.lastname: Song
keywords: Area under curve; Drug monitoring, Therapeutic; Pharmacodynamics; Vancomycin