The stability of 0.2-mg/mL glycopyrrolate injection in 6-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 glycopyrrolate injection 0, 1, 4, 7, 15, 30, 45, 60, and 90 days after preparation of the syringes. Benzyl alcohol, which was added as a preservative, did not interfere with the assay. The injection in plastic syringes was stable for up to 90 days at both ambient temperature and at 4 deg C. The pH of the glycopyrrolate injection did not change appreciably during the 90-day study period. These data indicate the stability of glycopyrrolate injection under the storage conditions investigated in this study.