title: Opioid-sparing effect of intravenous outpatient ketamine infusions appears short-lived in chronic-pain patients with high opioid requirements.
abstract: OBJECTIVE
  Ketamine is opioid-sparing. It attenuates the onset of opioid tolerance, and suppresses opioid-induced hyperalgesia. This study evaluated whether or not repeated outpatient infusions of intravenous ketamine reduced the amount of pain and the amount of opioid requirements for patients suffering with chronic, non-cancerous pain.
  
  
  METHODS
  Retrospective study
  
  
  METHODS
  Outpatient pain clinic
  
  
  METHODS
  We reviewed the records of 18 patients taking high doses of opioids chronically and nonetheless reporting poorly controlled pain. A comparison control group of 18 similar patients with high opioid requirements who were not given ketamine were selected from our clinic population.
  
  
  METHODS
  Intravenous ketamine infusions
  
  
  METHODS
  VAS pain scores and opioid use
  
  
  RESULTS
  Morphometric and demographic characteristics, baseline opioid use, and pain scores were similar in the ketamine and comparison groups. Five patients given ketamine experienced no benefit and discontinued treatment after 1-2 infusions. One patient developed a supraventricular arrhythmia which immediately resolved upon cessation of the infusion. And another, despite pain relief, felt overly-anxious and opted out. Eleven patients thus completed 3-6 weekly ketamine infusions. At 6 months, 5 patients maintained less than 50% of their baseline opioid use, while the remaining patients returned to the baseline opioid use or increased their requirements. There was no significant difference in pain scores at 6 months in patients who received ketamine infusions and control group patients.
  
  
  CONCLUSIONS
  Retrospective nature of the study
  
  
  CONCLUSIONS
  Outpatient intravenous ketamine infusions did not improve long-term pain scores in patients with high opioid requirements and only a few were able to substantially reduce opioid use. Considering infusion risks and cost of such outpatient treatment, ketamine infusions do not appear to be a feasible option for improving pain relief and decreasing opioid use in high-opioid requirement patients.
authors.affiliation: Departments of Pain Management and Outcomes Research, Cleveland Clinic, Cleveland, OH, USA. Kapural@ameritech.net
authors.forename: Leonardo
authors.initials: L
authors.lastname: Kapural
authors.forename: Miranda
authors.initials: M
authors.lastname: Kapural
authors.forename: Toula
authors.initials: T
authors.lastname: Bensitel
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
mesh_terms: D000328:Adult; D000368:Aged; D000700:Analgesics / Q000008:administration & dosage*; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000009:adverse effects; D002908:Chronic Disease; D004334:Drug Administration Schedule; D004357:Drug Synergism; D004359:Drug Therapy, Combination / Q000379:methods; D004361:Drug Tolerance / Q000502:physiology; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous / Q000379:methods; D007649:Ketamine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D010148:Intractable Pain / Q000188:drug therapy*; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000700:Analgesics; D000701:Analgesics, Opioid; D007649:Ketamine