Stability Study of Morphine and Baclofen Solution in Polypropylene Syringes

Abstract Background The association of morphine and baclofen is used for the treatment of spasticity related pain. Moving these patients is sometimes difficult. In order to transport these syringes for pump refilling, it could be interesting to demonstrate the stability of the mixture, and so to be able to ensure the best transport conditions of syringes. Methods A stability indicating UPLC-DAD method was developed and validated according to the ICH guidelines. Two mixtures of morphine and baclofen – a low concentration mixture (morphine 1 mg/mL – baclofen 0.08 mg/mL) and a high concentration mixture (morphine 10 mg/mL – baclofen 1.6 mg/mL) stored in 5±3 °C and 25±2 °C were evaluated for seven days and compared to the initial observed concentrations. Results The stability of the low and high mixture is demonstrated for both storage conditions for seven days thanks to relative concentrations (95 % confidence intervals of the mean of 3 samples) systematically positioned between 95 % and 105 %. No degradation product was observed during the stability study. Conclusion This study shows the stability of a weakly concentrated mixture and a highly concentrated mixture of morphine and baclofen. Extrapolation of these data to an intermediate mixture may be considered. Further studies will support this hypothesis. This result will allow the transport of the preparation under optimal conditions. Advance preparations for intrathecal pump refills could also be feasible.