Opioid-sparing effect of intravenous outpatient ketamine infusions appears short-lived in chronic-pain patients with high opioid requirements.
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.
Kapural
Leonardo
L
Departments of Pain Management and Outcomes Research, Cleveland Clinic, Cleveland, OH, USA. Kapural@ameritech.net
Kapural
Miranda
M
Bensitel
Toula
T
Sessler
Daniel I
DI
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
D000700:Analgesics; D000701:Analgesics, Opioid; D007649:Ketamine