title: The stability of a ketamine-morphine solution.
abstract: Recent advances in acute pain mechanisms and management have implicated the N-methyl D-aspartate receptor-ion channel complex in the development of postoperative hyperalgesia and acute opioid tolerance. N-methyl D-aspartate receptor antagonists such as ketamine have been used increasingly in clinical studies in an effort to minimize acute postoperative pain and reduce opioid requirements. A mixture of ketamine and an opioid administered in the same solution and syringe would be a practical and useful technique for postoperative epidural analgesia, continuous IV infusion, or patient-controlled IV analgesia. We investigated the stability of a morphine sulfate and racemic ketamine solution in saline at pH 5.5-7.5 over a period of 4 days. Our study demonstrates that the ketamine-morphine mixture at a clinically relevant concentration seems to be stable at room temperature, at a wide range of pH values, for at least 4 days.
  
  
  CONCLUSIONS
  Small-dose ketamine is used with increasing frequency in the acute postoperative setting as an adjunct to traditional opioid analgesics. We show that a racemic ketamine and morphine solution at a clinically relevant concentration seems to be stable at room temperature at a wide range of pH values for at least 4 days.
authors.affiliation: Department of Anesthesia and Pain Management, Toronto General Hospital, ON, Canada.
authors.forename: Roger
authors.initials: R
authors.lastname: Schmid
authors.forename: Gideon
authors.initials: G
authors.lastname: Koren
authors.forename: Julia
authors.initials: J
authors.lastname: Klein
authors.forename: Joel
authors.initials: J
authors.lastname: Katz
mesh_terms: D000700:Analgesics / Q000032:analysis; D000701:Analgesics, Opioid / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D004338:Drug Combinations; D004355:Drug Stability; D004356:Drug Storage; D006863:Hydrogen-Ion Concentration; D007649:Ketamine / Q000032:analysis; D009020:Morphine / Q000032:analysis; D012996:Solutions
chemical_list: D000700:Analgesics; D000701:Analgesics, Opioid; D004338:Drug Combinations; D012996:Solutions; D007649:Ketamine; D009020:Morphine