Stability studies of binary and ternary mixtures containing morphine, midazolam, levomepromazine and hyoscine butylbromide for parenteral administration

Abstract

Abstract Objetives Parenteral (intravenous or subcutaneous) administration is routinely used in palliative medicine because patients are not able to take drugs orally. To avoid excessive injections, several drugs are usually given in the same dose, but the stability of these drugs when mixed is not always known. The aim of this study was to evaluate the stability of several mixtures of drugs (morphine, midazolam, levomepromazine and hyoscine butylbromide) kept under different storage conditions. Methods Stability was evaluated on the basis of percentage of drug remaining, pH, change of colour and gas or precipitate formation. Key findings The most notable results of the study showed that levomepromazine is rapidly degraded in 0.9% NaCl in all cases, and at high concentrations, morphine can precipitate when stored at 4°C. Conclusions Mixtures containing levomepromazine are rapidly degraded under experimental conditions.