Stability of lidocaine hydrochloride injection at ambient temperature and 4 deg C in polypropylene syringes.

The stability of 20mg/mL lidocaine hydrochloride injection in 12-mL polypropylene syringes stored at ambient temperature and at 4 deg C for up to 90 days was investigated. A high-performance liquid-chromatographic stability-indicating assay was used to determine the concentration level of lidocaine hydrochloride injection at 0, 1, 4, 7, 15, 30, 45, 60, and 90 days after preparation of the syringes. Methylparaben, which was added as a preservative, did not interfere with the assay. The injections in plastic syringes were stable for up to 90 days at both ambient temperature and at 4 deg C. The pH of lidocaine hydrochloride injection did not change appreciable during the 90-day study period. These data indicate the stability of lidocaine hydrochloride under the storage conditions investigated in this study.