Objectives The compatibility of intravenous fluids with medications is of paramount concern to pharmacists and is an imperative component of ensuring patient safety. Data regarding the physical compatibility of medications with intravenous fluids has not been examined, or published with conflicting results or the concentrations studied were not consistent with current practice. Our objective was to determine the physical compatibility of ceftriaxone and cefepime in 0.45% sodium chloride, Ringer’s lactate solution, and Plasma-Lyte A.

Methods An in vitro analysis of the physical compatibility of ceftriaxone and cefepime at 10 mg/mL, 20 mg/mL, and 40 mg/mL concentrations was conducted in 0.45% sodium chloride, Ringer’s lactate solution, and Plasma-Lyte A. Admixtures were evaluated in triplicate at hours 0, 1, 5, 8, and 24. Physical compatibility was assessed by visual inspection, spectrophotometry, and pH analysis.

Results Ceftriaxone 40 mg/mL was found to be physically incompatible in 0.45% sodium chloride and Ringer’s lactate solution beyond 5 hours and in Plasma-Lyte A beyond 8 hours. Cefepime was found to be physically incompatible with all fluids and in all concentrations beyond 1 hour.

Conclusions This work contributes to the body of literature dedicated to the evaluation of intravenous drug and fluid physical compatibility by identifying demonstrable changes in admixtures containing 0.45% sodium chloride, Plasma-Lyte A, and Ringer’s lactate solution. Ceftriaxone should not be administered with 0.45% sodium chloride, Ringer’s lactated solution, or Plasma-Lyte A at selected concentrations and time points and cefepime is not considered to be physically compatible at 10 mg/mL, 20 mg/mL, or 40 mg/mL in any of the studied fluids beyond 1 hour.