title: An intravenous ketamine test as a predictive response tool in opioid-exposed patients with persistent pain.
abstract: Chronic pain patients who are treated with opioid therapy represent a significant challenge to medical professionals. When pain recurs in the face of a previously effective opioid regimen, treatment options include dose escalation, opioid rotation, drug holidays, and the addition of adjuvants. Some experts advocate the use of N-methyl-D-aspartate receptor (NMDA-R) antagonists to combat tolerance. Recently, the use of an intravenous (i.v.) ketamine infusion to predict the response to a dextromethorphan (DX) treatment trial has been described. In this study, 56 opioid-exposed patients with recurrent pain were treated with a low-dose (0.1mg/kg) i.v. ketamine test followed by a DX treatment course. Using previously designated cutoff values for a positive response to ketamine (67% or more pain relief) and DX (50% or more pain relief), the sensitivity, specificity, positive predictive value, and negative predictive value for an i.v. ketamine infusion to predict subsequent response to DX treatment were 72%, 68%, 52%, and 85%, respectively. The observed agreement between analgesic responses was 78%, indicating a highly significant correlation (r=0.54, P=0.0001). Subgroup classification revealed no significant differences in the response to either ketamine or DX treatment based on pain classification (i.e., nociceptive, neuropathic, or mixed) or placebo response. In contrast, a weaker correlation between ketamine and DX response was found in subjects requiring high-dose rather than low-dose opioid therapy. A significant correlation also was noted between the development of side effects for the two NMDA-R antagonists. Based on these results, we conclude that an i.v. ketamine test may be a valuable tool in predicting subsequent response to DX treatment in opioid-exposed patients. with persistent pain.
authors.affiliation: Pain Management Division, Department of Anesthesiology & Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA. scohen40@jhmi.edu
authors.forename: Steven P
authors.initials: SP
authors.lastname: Cohen
authors.forename: Shuxing
authors.initials: S
authors.lastname: Wang
authors.forename: Lucy
authors.initials: L
authors.lastname: Chen
authors.forename: Connie
authors.initials: C
authors.lastname: Kurihara
authors.forename: Geselle
authors.initials: G
authors.lastname: McKnight
authors.forename: Matthew
authors.initials: M
authors.lastname: Marcuson
authors.forename: Jianren
authors.initials: J
authors.lastname: Mao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000701:Analgesics, Opioid / Q000009:adverse effects / Q000627:therapeutic use*; D000778:Anesthetics, Dissociative / Q000009:adverse effects; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D007649:Ketamine / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000188:drug therapy*; D011237:Predictive Value of Tests; D055815:Young Adult
chemical_list: D000701:Analgesics, Opioid; D000778:Anesthetics, Dissociative; D007649:Ketamine