Stability of epidural opiate solutions in 0.9 per cent sodium chloride infusion bags

Abstract

Abstract The stability of pethidine 2.5mg/ml, and of a mixture of bupivacaine hydrochloride 1.25mg/ml and diamorphine hydrochloride 125μg/ml, in 500ml 0.9 per cent sodium chloride infusion bags was determined. Samples of the solutions were stored uncovered at room temperature, exposed to natural and artificial light, for 24 and 28 days, respectively. No colour change, crystallisation or precipitation was observed, and although the mean pH of the bupivacaine and diamorphine mixtures increased slightly, the mean pH of the pethidine samples remained essentially unchanged. The only significant (P < 0.05) change in potency was a reduction in diamorphine concentration by a mean of 8.22 per cent after 28 days, which is in accordance with other reports on diamorphine degradation. Thus pethidine 2.5mg/ml in 500ml 0.9 per cent sodium chloride infusion bags is stable for at least 24 days at room temperature, and a mixture of bupivacaine hydrochloride 1.25mg/ml and diamorphine hydrochloride 125μg/ml in 500ml 0.9 per cent sodium chloride infusion bags is stable (less than 10 per cent loss of potency) for 28 days at room temperature. Both these solutions could, therefore, be prepared in pharmacy central intravenous additive units and supplied to hospital wards as 500ml infusion bags for use in epidural analgesia following surgery. As each bag would provide nearly three days' worth of analgesic, the risk of infection and the nursing workload should both be reduced.