Stability of intramuscular injection of Ertapenem combined with Lidocaine stored in polyethylene syringes at 4 ºC and -20ºC

Ertapenem is beta-lactam-type antibiotic with an exceptionally broad spectrum of activity, demonstrating broad-spectrum antimicrobial activity against many Gram-positive and -negative aerobes and anaerobes and is resistant to nearly all beta-lactamases. Ertapenem mixed with lidocaine can be administered intramuscularly, of great value as an outpatient antimicrobial therapy. However, the stability of this mixture has never been studied over time. The objective of this study was to evaluate the stability of 1g of ertapenem diluted in a 1% aqueous solution of lidocaine hydrochloride in a total volume of 3,2 mL stored in polyethylene syringes at 4ºC and -20ºC. Each preparation was analyzed using nuclear magnetic resonance method at the following time points: 0, 11 and 28 days. Dilutions were also observed for changes in appearance was tested at each time point. Syringes stored at -20ºC did not lead to any observable decomposition byproducts at least on day 11. Nevertheless, conservation at 4ºC for 11 days led to observed degradation byproducts in the solution.