Extended stability of meropenem in 0.9% sodium chloride injection stored at 23-25 °C

Meropenem is a broad-spectrum antimicrobial used to treat a wide variety of pathogens. In clinical practice, meropenem is frequently administered as an extended infusion. However, the stability of meropenem at room temperature when diluted in 0.9% sodium chloride injection ("normal saline" [NS]) is 1 hour per the package insert. Therefore, the concentration of meropenem during the extended infusion may decline to suboptimal levels due to degradation. The objective of this study was to determine the stability of meropenem diluted in bags of NS and stored at 23-25 °C.

Meropenem 1-g vials were used to prepare 13 mg/mL solutions via aseptic compounding that were stored at 23-25 °C. Samples at 0-, 2-, 4-, 6-, 12-, and 24-hour time points were collected and the meropenem concentration was determined using high-performance liquid chromatography. Data was presented in triplicate measurements of 3 independent drug preparations. Samples were considered stable when the percentage remaining concentration was maintained above the 90% threshold stated in the United States Pharmacopeia-National Formulary monograph.

Chemical stability is typically defined as 90% or more of the drug remaining in the preparation. All sample solutions of meropenem remained above 90% of the initial drug concentration threshold through the 12-hour time point (mean concentration, 92.72%), with a linear decrease in concentration over time. At the 24-hour time point, the remaining concentration of meropenem fell below the 90% threshold (to a mean of 86.65%).

Meropenem can remain stable for up to 12 hours when formulated in a polyvinyl chloride bag containing 100 mL of NS stored at 23-25 °C.