title: Visual and absorbance analyses of admixtures containing vancomycin and piperacillin-tazobactam at commonly used concentrations.
abstract: OBJECTIVE
  The compatibility of vancomycin and piperacillin-tazobactam in concentrations typically used in extended-infusion dosing schemes was evaluated.
  
  
  METHODS
  Piperacillin-tazobactam was reconstituted and diluted to concentrations of 33.75, 45, 50, 60, 67.5, 80, and 90 mg/mL. Vancomycin was diluted to concentrations of 4-8, 10, and 12 mg/mL. The resultant admixtures were visually observed after preparation against black and white backgrounds each hour between hours 1 through 4 and after 24 hours. Frozen products of each medication and brand-name Zosyn powder for reconstitution also were studied. Each combination of products and concentrations was tested for precipitation using simulated Y-site administration. Absorbance and microscopic analyses were performed to discern less perceptible incompatibilities in combinations that did not result in visual precipitation. Changes in absorbance were evaluated using two-way repeated-measures analysis of variance with post hoc Bonferroni corrections.
  
  
  RESULTS
  No tested concentrations of piperacillin-tazobactam showed precipitations with vancomycin up to concentrations of 7 mg/mL. Piperacillin-tazobactam 80-90 mg/mL formed reversible precipitation with vancomycin 8 mg/mL. All tested concentrations of piperacillin-tazobactam formed a reversible precipitate with vancomycin 10 mg/mL. Irreversible precipitation was noted with all combinations of piperacillin-tazobactam and vancomycin 12 mg/mL. No significant changes in absorbance analyses were identified for all tested piperacillin-tazobactam concentrations and vancomycin 4-10 mg/mL compared with 0.9% sodium chloride injection (p > 0.05). Similar results were observed using frozen preparations and brand-name Zosyn.
  
  
  CONCLUSIONS
  Visual, microscopic, and absorbance analyses showed no evidence of incompatibility when piperacillin-tazobactam 33.75-90 mg/mL was combined with vancomycin ≤7 mg/mL. Reversible and irreversible precipitates formed when piperacillin-tazobactam was combined with vancomycin ≥8 mg/mL.
authors: Department of Pharmacy Practice, Chicago College of Pharmacy, Midwestern University, Downers Grove, IL, and Department of Pharmacy, Northwestern Memorial Hospital, Chicago, IL.
authors: J Nicholas
authors: JN
authors: O'Donnell
authors: Department of Pharmaceutical Science, Chicago College of Pharmacy, Midwestern University, Downers Grove, IL.
authors: Natarajan
authors: N
authors: Venkatesan
authors: Chicago College of Pharmacy, Midwestern University, Downers Grove, IL.
authors: Malav
authors: M
authors: Manek
authors: Department of Pharmacy Practice, Chicago College of Pharmacy, Midwestern University, Downers Grove, IL, and Department of Pharmacy, Northwestern Memorial Hospital, Chicago, IL.
authors: Nathaniel J
authors: NJ
authors: Rhodes
authors: Department of Pharmacy Practice, Chicago College of Pharmacy, Midwestern University, Downers Grove, IL, and Department of Pharmacy, Northwestern Memorial Hospital, Chicago, IL. mscheetz@nm.org.
authors: Marc H
authors: MH
authors: Scheetz
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000737:chemistry*; D011232:Chemical Precipitation; D004339:Drug Compounding / Q000379:methods; D004344:Drug Incompatibility; D006801:Humans; D010397:Penicillanic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry; D010878:Piperacillin / Q000008:administration & dosage / Q000737:chemistry; D000077725:Piperacillin, Tazobactam Drug Combination; D012965:Sodium Chloride / Q000737:chemistry; D013997:Time Factors; D014640:Vancomycin / Q000008:administration & dosage / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D000077725:Piperacillin, Tazobactam Drug Combination; D012965:Sodium Chloride; D014640:Vancomycin; D010397:Penicillanic Acid; D010878:Piperacillin