title: Lack of analgesia by oral standardized cannabis extract on acute inflammatory pain and hyperalgesia in volunteers.
abstract: BACKGROUND
  Cannabinoid-induced analgesia was shown in animal studies of acute inflammatory and neuropathic pain. In humans, controlled clinical trials with Delta-tetrahydrocannabinol or other cannabinoids demonstrated analgesic efficacy in chronic pain syndromes, whereas the data in acute pain were less conclusive. Therefore, the aim of this study was to investigate the effects of oral cannabis extract in two different human models of acute inflammatory pain and hyperalgesia.
  
  
  METHODS
  The authors conducted a double-blind, crossover study in 18 healthy female volunteers. Capsules containing Delta-tetrahydrocannabinol-standardized cannabis extract or active placebo were orally administered. A circular sunburn spot was induced at one upper leg. Heat and electrical pain thresholds were determined at the erythema, the area of secondary hyperalgesia, and the contralateral leg. Intradermal capsaicin-evoked pain and areas of flare and secondary hyperalgesia were measured. Primary outcome parameters were heat pain thresholds in the sunburn erythema and the capsaicin-evoked area of secondary hyperalgesia. Secondary measures were electrical pain thresholds, sunburn-induced secondary hyperalgesia, and capsaicin-induced pain.
  
  
  RESULTS
  Cannabis extract did not affect heat pain thresholds in the sunburn model. Electrical thresholds (250 Hz) were significantly lower compared with baseline and placebo. In the capsaicin model, the area of secondary hyperalgesia, flare, and spontaneous pain were not altered.
  
  
  CONCLUSIONS
  To conclude, no analgesic or antihyperalgesic activity of cannabis extract was found in the experiments. Moreover, the results even point to the development of a hyperalgesic state under cannabinoids. Together with previous data, the current results suggest that cannabinoids are not effective analgesics for the treatment of acute nociceptive pain in humans.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine A, Medical University of Vienna, Vienna, Austria. birgit.kraft@meduniwien.ac.at
authors.forename: Birgit
authors.initials: B
authors.lastname: Kraft
authors.forename: Nathalie A
authors.initials: NA
authors.lastname: Frickey
authors.forename: Rainer M
authors.initials: RM
authors.lastname: Kaufmann
authors.forename: Marcus
authors.initials: M
authors.lastname: Reif
authors.forename: Richard
authors.initials: R
authors.lastname: Frey
authors.forename: Burkhard
authors.initials: B
authors.lastname: Gustorff
authors.forename: Hans G
authors.initials: HG
authors.lastname: Kress
mesh_terms: D000208:Acute Disease; D000284:Administration, Oral; D000328:Adult; D000698:Analgesia / Q000379:methods*; D002188:Cannabis; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy* / Q000473:pathology* / Q000503:physiopathology; D018836:Inflammation Mediators / Q000008:administration & dosage* / Q000302:isolation & purification; D010146:Pain / Q000188:drug therapy* / Q000503:physiopathology; D010147:Pain Measurement / Q000187:drug effects / Q000379:methods; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D010936:Plant Extracts / Q000008:administration & dosage* / Q000302:isolation & purification
chemical_list: D018836:Inflammation Mediators; D010936:Plant Extracts