Compatibility and Physico-Chemical Stability of Six Intravenous Mixtures for Postoperative Multimodal Analgesia

Analgesic mixtures of tramadol and ketamine with adjuvants (dexketoprofen or ketorolac, with or without methadone) showed physicochemical stability for 48 hours at room temperature and up to 30 days at 2°-8°C in polyolefin bags. However, the combination of tramadol, dexketoprofen, and methadone was unstable in both tested elastomeric devices due to methadone adsorption, making it unsuitable for clinical use. These findings underscore the critical role of container material in drug stability.