Physico-chemical stability of butorphanol-tramadol and butorphanol-fentanyl patient-controlled analgesia infusion solutions over 168 hours.

This study was to investigate the physical and chemical compatibility of butorphanol with tramadol or fentanyl in 0.9% sodium chloride injections for patient controlled analgesia administration. The solutions were prepared in polyvinyl chloride (PVC) infusion bags and stored without protected from light exposure at room temperature (25 degrees C) or refrigerated (4 degrees C). Over a period of 168 hours, stabilities were determined by visual inspection, pH measurement, and high-pressure liquid chromatography (HPLC) assay of drug concentrations. At both temperatures, admixtures of butorphanol-tramadol and butorphanol-fentanyl were clear in appearance, and no color change or precipitation was observed during the study period. The maximum losses obtained were lower than 5% for the three drugs after 168 hours of storage. The results indicate that, at ambient or refrigerated storage conditions, the drug mixtures of butorphanol-tramadol and butorphanol-fentanyl in 0.9% sodium chloride injections were physically and chemically stable for at least 168 hours when stored in PVC syringes.