[Chemical Stability after Mixing Continuous Infusion Drugs Used to Treat Cardiogenic Shock]

During the treatment of cardiogenic shock, various continuous infusion drugs are used simultaneously. However, administration from the same route may result in stability changes due to mixing of drugs. In addition, stability tests after mixing more than three types of drugs have hardly been conducted. In this study, noradrenaline, milrinone, dobutamine hydrochloride, and landiolol hydrochloride were used to evaluate the chemical stability of the mixture. Chemical stability was evaluated by measuring the change in each drug concentration over time and calculating the content. The concentration of each drug was measured using an optimized gradient elution method by HPLC. In a four-drug mixed sample, noradrenaline, milrinone, dobutamine hydrochloride, and landiolol hydrochloride had retention times of 2.1 min, 5.2 min, 9.3 min, and 11.9 min, respectively. The concentration immediately after mixing each drug was almost the same as the theoretical concentration at the time of mixing each drug. Furthermore, noradrenaline, milrinone, and dobutamine hydrochloride concentrations were maintained up to 99% in each drug mixture until 24 h after mixing all the samples. However, the content of landiolol hydrochloride was 90% or less 24 h after mixing, except for two types of mixed solutions with dobutamine hydrochloride. This result suggested that landiolol hydrochloride was being degraded owing to acidic conditions. The results of this study suggest that noradrenaline, milrinone, and dobutamine hydrochloride can be administered from one route, while it is recommended that landiolol hydrochloride be administered from another route.