Stability of diazepam injection repackaged in glass unit-dose syringes

The stability of diazepam injection repackaged in disposable glass syringes and stored at room and refrigerator temperatures was studied. Thirty-nine 1.5-ml syringes were filled with 1.1 ml diazepam injection 5-mg/ml. All syringes were stored in light-resistant bags on their sides so that the solution was in contact with the rubber stoppers on both ends. Samples were assayed with a stability-indicating HPLC method for diazepam and its degradation product, 2-methylamino-5-chloro-benzophenone (MACB), after 30, 60, and 90 days of storage at 30 degrees C and 4 degrees C. At 90 days, the diazepam injection stored at 4 degrees C retained 97.4 +/- 1.6% of its original potency; samples stored at 30 degrees C retained 92.4 +/- 1% of their original potency. Apparent sorption to rubber syringe components led to a decrease in the concentration of both diazepam and MACB. The decrease in diazepam was a function of storage time and temperature; however, the disappearance of MACB from the syringes was a function of only time. Diazepam injection is chemically stable as 5-mg doses in disposable glass syringes for 90 days when stored at 4 degrees C or 30 degrees C. However, refrigeration is recommended.