Objective Bupivacaine hydrochloride (BH) and ketorolac tromethamine (KT) are commonly used in parenteral admixtures to manage postoperative pain. However, stability and compatibility data for these admixtures applicable to current practice are limited, posing the patient to potential risk.

Methods The stability of BH/KT admixtures in commonly used parenteral fluids was studied in Eppendorf tubes and glass vials at ambient room temperature using a newly developed and validated stability-indicating high-performance liquid chromatography (HPLC) method capable of the simultaneous quantification of both drugs. The chemical compatibility of BH/KT was assessed using Fourier transform infrared spectroscopy (FTIR) and thermal analysis. Additionally, the validity of the developed HPLC method for the quantification of BH/KT in human plasma was evaluated.

Results BH and KT demonstrated <10% loss of their initial concentrations when prepared in Ringer, normal saline or dextrose solution at ambient temperature for up to 4 weeks. FTIR and thermal analysis demonstrated mild intermolecular interactions between BH and KT in solution, with no evidence of incompatibility. The developed HPLC method demonstrated satisfactory accuracy and precision for the simultaneous quantification of BH and KT in human plasma over the range of 0.2–3.2 µg·mL^-1.

Conclusion BH/KT parenteral admixtures are chemically stable for a period of 4 weeks when stored at room temperature. The stability-indicating HPLC method is valid for BH/KT simultaneous determination in human plasma, facilitating pharmacokinetics studies.