title: The effect of hydromorphone therapy on psychophysical measurements of the descending inhibitory pain systems in patients with chronic radicular pain.
abstract: OBJECTIVE
  Conditioned pain modulation (CPM) and offset analgesia (OA) are considered to represent paradigms of descending inhibitory pain modulation in humans. This study tested the effects of hydromorphone therapy on descending inhibitory pain modulation, as measured by changes from baseline in the magnitudes of CPM and OA.
  
  
  METHODS
  Prospective evaluation.
  
  
  METHODS
  Institute of Pain Medicine, Rambam Health Care Campus.
  
  
  METHODS
  Patients with chronic radicular pain.
  
  
  METHODS
  Thirty patients received 4 weeks of oral hydromorphone treatment at an individually titrated dose (mean ± standard deviation dose of 11.6 ± 4.8 mg/day). CPM and OA were assessed before and after hydromorphone treatment. CPM was assessed by subtracting the response to a painful phasic heat stimulus administered simultaneously with a conditioning cold pain stimulus, from the response to the same heat stimulus administered alone. The OA paradigm consisted of a three-temperature stimuli train (T1 = 49°C [5 seconds], T2 = 50°C [5 seconds], and T3 = 49°C [20 seconds]). The magnitude of OA was quantified by subtracting minimal pain scores obtained during T3 from the maximal pain scores obtained during T2.
  
  
  RESULTS
  CPM scores changed from a baseline of 17.7 ± 20.6 to 21 ± 20.4 following treatment, and OA scores changed from 7.8 ± 20.5 to 9.7 ± 14.6. Wilcoxon signed rank test indicated that these changes were not significant (CPM: P = 0.22; OA: P = 0.44). McNemar test revealed that the percentage of patients who exhibited a change in the direction of CPM or OA in response to hydromorphone treatment was not significant (CPM: P = 0.37; OA: P = 0.48).
  
  
  CONCLUSIONS
  These results suggest that the descending inhibitory pain modulation, as manifested in humans by CPM and OA, is unlikely to be mediated by hydromorphone therapy.
authors.affiliation: Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel; Institute of Pain Medicine, Rambam Health Care Campus, Haifa, Israel.
authors.forename: Erica
authors.initials: E
authors.lastname: Suzan
authors.forename: Roi
authors.initials: R
authors.lastname: Treister
authors.forename: Dorit
authors.initials: D
authors.lastname: Pud
authors.forename: May
authors.initials: M
authors.lastname: Haddad
authors.forename: Elon
authors.initials: E
authors.lastname: Eisenberg
mesh_terms: D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000627:therapeutic use*; D059350:Chronic Pain / Q000188:drug therapy*; D003213:Conditioning, Psychological / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D004091:Hydromorphone / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D010812:Physical Stimulation; D011601:Psychophysics; D011843:Radiculopathy / Q000188:drug therapy*; D055815:Young Adult
chemical_list: D000701:Analgesics, Opioid; D004091:Hydromorphone
keywords: Conditioned Pain Modulation (CPM); Hydromorphone; Neuropathic Pain; Offset Analgesia (OA); Opioids; Pain Pathways