Stability of injections containing diamorphine and midazolam in plastic syringes

Abstract

The stability of mixtures containing diamorphine hydrochloride, 10 or 500mg, and midazolam, 10 or 75mg, in 15ml water for injections, stored in three piece plastic syringes, was investigated using a stability-indicating HPLC method. Results indicated that diamorphine showed greater degradation than midazolam, which was relatively stable over the study period of 14 days at ambient temperature. Rates of degradation of diamorphine were estimated by linear regression analysis. The estimated values for the time to reach 10 per cent degradation in solutions containing 10 mg and 500mg diamorphine were 15.9 and 22.2 days, respectively. There was no evidence of physical incompatibility in any of these mixtures. It is recommended from these data that mixtures containing diamorphine hydrochloride and midazolam within the concentration ranges tested, and diluted in water for injections, may be assigned shelf lives of 14 days when stored at ambient temperature.