Stability of Diluted Intravenous Metronidazole in 0.9% Sodium Chloride

Objectives: The stability of metronidazole has been demonstrated for high concentration and short-term storage. Little is known about the stability of its dilutions in 0.9% sodium chloride at concentrations relevant for neonatal clinical practice. This study aimed to evaluate the stability of metronidazole solutions at concentrations of 0.1 and 0.6 mg/mL, stored at room temperature and under refrigeration for 24 and 48 hours in 0.9% sodium chloride. Methods: Metronidazole concentrations were measured using a high-performance liquid chromatography method with ultraviolet detection. Calibration curves were linear over the concentration range of 0.025 to 1.25 mg/mL. Stability was defined as retention of 90% to 110% of the initial concentration. Results were expressed as percent deviation from the initial (0 hour) concentration, where 0% corresponds to the initial value (100%). Key findings: At room temperature, mean relative accuracy ranged from 0.7 ± 1.8% to 5.5 ± 1.1%. Under refrigeration, it ranged from −5.5 ± 4.0% to 3.5 ± 1.8%. All samples remained within the pharmacopeial acceptance range (90%-110%) of the initial concentration, corresponding to deviations within ±10%. Conclusions: Metronidazole concentrations of 0.1 and 0.6 mg/mL remained within the predefined acceptance limits for up to 48 hours in 0.9% w/v sodium chloride at 6°C and 22°C, supporting safe short-term storage in neonatal practice.