Physical stability of highly concentrated injectable drugs solutions used in intensive care units

Summary Background The intensive care department of the institution use drug solutions within higher concentration to avoid fluid overload. The purpose of the study is to prove the physical stability of different injectable drugs within high concentration (amiodarone 25 mg/mL, isosorbide 0.60 mg/mL, lorazepam 0.16 mg/mL, noradrenalin 0.120 and 0.240 mg/mL, salbutamol 0.06 mg/mL and sodium valproate 12 mg/mL) to ensure the patients safety. Methods Five of 30 or 50 mL polypropylene syringes were prepared for each solution under aseptic conditions and stored at room temperature. Immediately after the preparation (hour 0) and after 1, 4, 8, 24 and 48 hours, 2 mL of each solution were withdrawn from each syringe and placed in glass tubes to proceed to the stability test. All specimens were visually inspected in front of a black and of a white background and aliquots of each solution were centrifuged to proceed to microscopic inspection with a ten-fold magnification. The pH of each solution was measured with glass electrode pH-meter (Inolab level 1, WTW Weilhem, Germany with biotrode electrode, Hamilton, Bonaduz, Switzerland) and spectrophotometric measurements (Genesys 10 series, New-York, USA) were performed at three wavelengths (350, 410 and 550 nm) to avoid the apparition of turbidity. Results For all the drugs included in the study, there was no significant change in pH, no color change, no turbidity or opacity and no precipitation observed in the solutions during the storage at room temperature for 48 hours. No microaggregates were detected by microscope neither revealed by a change of absorbance. Conclusion Within these limits, the preparations of amiodarone in 5% glucose polypropylene syringes and isosorbide, lorazepam, noradrenalin, salbutamol, valproate in 0.9% sodium chloride polypropylene syringes are physically stable at room temperature for 48 hours. These results allow us to consider a study of chemical stability by high-performance liquid chromatography (HPLC).