[Chemical compatibility of ketamine and midazolam in infusion solutions]

The chemical compatibilities of intravenous (i.v.) solutions containing ketamine and midazolam were investigated by UV/VIS spectroscopy, IR spectroscopy, and high-performance liquid chromatography (HPLC). The isotonic solutions used were NaCl 0.9%, fructose 5%, and glucose 5%. The concentrations of additives were 500 mg ketamine and 45 mg midazolam per liter i.v. solution. Comparison of the UV/VIS and IR spectroscopic measurements with spectra from the literature demonstrated, that the substances were pure, e.g. without larger impurities. The HPLC measurements were performed immediately after preparation of the solution and repeated after 6, 25, 50, 75 and 97 h. It was shown that there was no concentration decrease of ketamine and midazolam in the i.v. solutions within an experimental error of 1.5% and within 100 h. Reactions in the i.v. solutions with smaller than 1.5% conversion can not be excluded. We recommend that the prepared i.v. solution be used within 24 h.