Stability of generic brands of meropenem reconstituted in isotonic saline

Meropenem is a relatively unstable compound when dissolved. Currently, all available data have been derived from tests on the original product from Astrazeneca, and it is unsure if these data can be extrapolated to the stability of other commercially available vials. The aim of this study was therefore to assess the stability of four different brands of meropenem to be used as a prolonged or continuous infusion.

Commercially available meropenem vials were reconstituted and mixed with 0.9% sodium chloride to produce solutions with concentrations of 10.20 and 40 mg/mL in polypropylene syringes, which were kept at 25 °C. Samples were taken immediately after preparation and up to 12 hours. Solutions retaining >90% of the initial concentration were considered stable.

The stability was concentration-dependent. At 25 °C, all 10 and 20 mg/mL solutions were stable for 12 hours in 0.9% sodium chloride, while the 40 mg/mL solutions were stable for a maximum of 8 hours. Stability of the different vials of meropenem was comparable for the time period tested (related samples Friedman's two way of analysis of variance by ranks, P=0.282).

All tested commercially available vials of meropenem in a concentration of 10 and 20 mg/mL were stable for 12 hours at 25 °C when diluted in 0.9% sodium chloride. The 40 mg/mL solutions were stable for a maximum of 8 hours. This report is the first to show equivalent stability between different commercially available vials of meropenem.