Stability of morphine hydrochloride in a portable pump reservoir

The stability of morphine hydrochloride in an admixture with sodium chloride 0.9% injection in a portable pump reservoir was investigated. Duplicate samples containing morphine hydrochloride 0.5, 1.5 and 2.5 mg/ml were stored in original 100 ml plastic drug reservoirs at 32 degrees C for 60 days. An amount of 3 ml was removed immediately after preparation and at fixed intervals in the weeks after. All samples were tested for loss of vehicle, for appearance of precipitation and for change in colour or pH. Furthermore, they were analysed for drug concentration using high pressure liquid chromatography. No precipitation or change in colour was observed in any of the sample admixtures. There was no change in the pH values of any of the morphine hydrochloride concentrations from day 4 and later on. Only between day 1 and day 4 a slight, but not significant rise could be detected. There was no loss of morphine hydrochloride of any importance at any concentration in the samples over 60 days when corrected for loss of vehicle. Loss of vehicle (0.8 +/- 0.1 ml a week), on the other hand, gave a rise in morphine hydrochloride concentration.