title: Elevations of urinary pH may lower vancomycin serum concentration.
abstract: OBJECTIVE
  This study investigated endogenous factors that may increase the elimination of vancomycin (VCM) in adult methicillin-resistant Staphylococcus aureus (MRSA) patients with pneumonia.
  
  
  METHODS
  48 patients (32 men and 16 women) admitted to the National Hospital Organization Kumamoto Medical Center for pneumonia due to MRSA were evaluated. VCM (500 - 2,000 mg/dose) was administered intravenously for 60 - 120 min at 8- - 12-h intervals. The dose of VCM prescribed was determined based on the treatment guidelines of the Infectious Diseases Society of America and was dependent on a patient's creatinine clearance.
  
  
  RESULTS
  Univariate analysis identified that potassium value (K) (p = 0.081) and urinary pH (p = 0.026) were possibly associated with decreased VCM concentration. Multivariate analysis confirmed that urinary pH was an independent risk factor for VCM clearance (p = 0.029). VCM clearance in patients with a urine pH of 8 was significantly higher (p = 0.032) than in patients with a urinary pH of 5. As urinary pH increased in alkalinity, a greater decrease in VCM concentrations was observed.
  
  
  CONCLUSIONS
  Elevation of urinary pH promotes the urinary excretion of VCM, likely by promoting the dissociation of the carboxyl group of VCM. Thus, in the clinical setting, urinary pH should be measured and considered when determining dosage, as it may affect the VCM blood concentration.
authors.affiliation: Department of Pharmacy, National Hospital Organization Beppu Medical Center, Oita, Department of Pharmacy, Department of Hematology, National Hospital Organization Kumamoto Medical Center, Kumamoto, Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama, Toyama, and Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Hiraki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Tsuji
authors.forename: Naoko
authors.initials: N
authors.lastname: Yasumori
authors.forename: Masahisa
authors.initials: M
authors.lastname: Nagano
authors.forename: Daisuke
authors.initials: D
authors.lastname: Inoue
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Kamimura
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Karube
authors.forename: Fumio
authors.initials: F
authors.lastname: Kawano
mesh_terms: D000900:Anti-Bacterial Agents / Q000097:blood*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016015:Logistic Models; D008297:Male; D014556:Urine; D014640:Vancomycin / Q000097:blood*
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin