Stability of an epidural analgesic solution containing adrenaline, bupivacaine and fentanyl

Background: A low dose solution of adrenaline 2 mu g . ml(-1), fentanyl 2 m u g . ml(-1) and bupivacaine 1 mg . ml(-1) has been reported to give superi or pain control when used for epidural analgesia after major surgery. The p resent paper describes the compounding and chemical stability of this tripl e-component solution during storage and use. Methods: Sterile triple-component concentrates (11X) were diluted by the us e of gas isolator technology to give ready-to-use infusion solutions. Eight solutions were analysed by reverse phase high-performance liquid chromatog raphy (HPLC) methods, and assays were performed on 1, 45, 90 and 180 days a fter storage at 2-8 degrees C. After 180 days the solutions were subsequent ly stored at 22C for four days before they were reanalysed. HPLC quantifica tion of adrenaline was also performed on samples from solutions given to 28 different patients. Results: The concentration of adrenaline and fentanyl decreased approximate ly 3.5% from 1 to 180 days at 4 degrees C and four days at 22 degrees C. Th e corresponding figure for bupivacaine was an apparent increase by 2.4% in concentration. No absorption to the polypropylene plastic bags of fentanyl and bupivacaine was detected. None of the 28 samples derived from used infu sion bags contained less than 95% of the declared content of adrenaline. Conclusions: The triple-component epidural analgesic solution remained stab le during six months of cold storage, followed by four days of storage at r oom temperature. No significant degradation of adrenaline tvas observed in infusion solutions returned from the wards.