Extended stability of oxytocin in common infusion solutions

The objective of this study was to evaluate the physical and chemical stability of oxytocin 0.08 U/mL admixed in 5% dextrose injection, 0.9% sodium chloride injection, and lactated Ringer's injection bags. Triplicate test samples of oxytocin 0.08 U/mL in each infusion solution were prepared by adding the required amount of oxytocin injection to bags of the three infusion solutions. The samples were stored protected from light and evaluated at appropriate intervals for up to 90 days at room temperature (near 23 deg C). Physical stability was assessed by using an evaluation procedure that included both turbidimetric measurement and visual inspection. Chemical stability was assessed by using a stability-indicating high-performance liquid chromatographic analytical technique and was based on the determination of drug concentrations initally and at appropriate intervals over the study period. The oxytocin admixtures in 5% dextrose and 0.9% sodium chloride were clear and colorless when viewed in normal fluorescent room light and when viewed with a Tyndall beam initially and throughout 90 days. Measured turbidity was low initially and exhibited little change throughout the study. High-performance liquid chromatographic analysis revealed that little or no decomposition occurred in the samples. Oxytocin in the infusion solutions remained stable at room temperature for 90 days. The lactated Ringer's injection samples remained clear and colorless for up to 28 days. However, after that time a small amount of white fluffy microprecipitate developed in two of the three samples by the 35-day observation point. High-performance liquid chromatographic analysis revealed that oxytocin remained stable in lactated Ringer's injection for 28 days at room temperature; substantial losses of oxytocin occurred in all three samples after that time, with about 10% loss at 35 days and up to 21% loss at 60 days. Oxytocin 0.08 U/mL in 5% dextrose injection or 0.9% sodium chloride injection is physically and chemically stable for at least 90 days at room temperature. However, oxytocin in lactated Ringer's injection should be restricted to a use period no greater than 28 days at room temperature to avoid microprecipitate formation and drug loss.