Stability of dopamine hydrochloride 0·5 mg/mL in polypropylene syringes

Objective: To determine the stability of dopamine hydrochloride diluted to 0·5 mg/mL in isotonic glucose infusion and stored in 50 mL polypropylene syringes from two different suppliers.

Methods: Polypropylene syringes containing dopamine hydrochloride 0·5 mg/mL were stored protected from light at 25 °C/60% relative humidity for 1 week, at 4 °C/ambient humidity for 3 months and at −20 °C/ambient humidity for 6 months. Samples were periodically withdrawn and the concentration of dopamine hydrochloride determined using a stability-indicating high-performance liquid chromatography method. The appearance of the solutions with respect to colour, clarity and precipitation was studied and the pH of the solutions measured.

Results: The concentration of dopamine hydrochloride in the solutions remained at least 95% of the initial concentration after storage at 25 °C for 1 week and at 4 °C for 3 months. Variation in dopamine concentration was observed in syringe samples, stored frozen, from two suppliers. The mean concentration was ≥95% for product stored in syringes from Codan and ≥90% of initial concentration when stored in syringes from Braun. In some of the syringes from Braun, the concentration was lower than 90%. The samples in all syringes had to be homogenized after thawing to give a uniform solution. There were no other evident changes in the physical appearance or pH of the solutions during the study.

Conclusion: Dopamine hydrochloride 0·5 mg/mL in isotonic glucose solution is stable when protected from light for 1 week at 25 °C/60% relative humidity and for 3 months at 4 °C/ambient humidity in Codan and Braun syringes. The cause of content variability observed in solutions stored frozen in Braun syringes needs further investigation. Braun syringes should not be used if the product is to be frozen. The stability of the frozen product, in Codan syringes is 6 months.