Feasibility and stability of metaraminol in pre‐filled syringes

Background Metaraminol 10 mg/ mL injection is often diluted with sodium chloride 0.9% and pre‐drawn into syringes by anaesthetists for use in the management of intraoperative hypotensive crisis. The 10 mg/ mL ampoule presentation poses a significant safety hazard since the entire content needs to be drawn into a syringe and then diluted so that 0.5 mg doses may be administered. There have been incidents where 10 mg rather than the intended 0.5 mg have been administered to the patient. Additionally the pre‐drawn metaraminol is discarded at the end of the case if not used, which results in significant wastage. A pre‐filled syringe presentation of metaraminol will improve patient safety and reduce wastage. Aim To determine the feasibility and stability of metaraminol 3 mg/6 mL pre‐filled syringes. Method Metaraminol 10 mg/ mL injections were diluted with sodium chloride 0.9% and repacked into 3 mg/6 mL syringes. Syringes were stored at three different conditions: room temperature, refrigerated and frozen. Metaraminol syringes from each storage condition were analysed in triplicate, using a validated high performance liquid chromatography assay on Days 0, 1, 7, 14, 28, 58, 91, 126, 161, 189, 252, 315 and 378. A 5% change limit was used to assess stability. Results Metaraminol 3 mg/6 mL syringes were stable when analysed up to Day 378 with levels remaining at 95.4 +/− 0.4% of initial concentration for both room temperature and refrigerated storage. In the frozen storage arm, samples that were defrosted immediately and 7 days prior to sampling exceeded the 5% limit by day 315 and day 378, respectively. Conclusion Metaraminol 3 mg/6 mL pre‐filled syringes are stable for up to 378 days when stored at room temperature, or refrigerated and this presentation is feasible for use in the operating theatre.