title: Differential effect of intravenous S-ketamine and fentanyl on atypical odontalgia and capsaicin-evoked pain.
abstract: Atypical odontalgia (AO) is an intraoral pain condition of currently unknown mechanisms. In 10 AO patients and 10 matched healthy controls, we examined the effect of intravenous infusion of an N-methyl-D-aspartate (NMDA) receptor antagonist S-ketamine and a mu-opioid agonist fentanyl on spontaneous AO pain and on an acute intraoral nociceptive input evoked by topical application of capsaicin. The drugs were administered in a randomized, placebo-controlled, cross-over manner. Furthermore, measures of intraoral sensitivity to mechanical and thermal quantitative sensory testing (QST) including temporal summation were compared between groups and sides. Both drugs failed to produce an analgesic effect on spontaneous AO pain, but fentanyl effectively reduced capsaicin-evoked pain. AO patients showed increased sensitivity to capsaicin and heat pain, but no significant differences in cold and mechanical sensitivity compared with healthy controls. No side-to-side differences in QST measures were found in AO patients. The present study demonstrates that AO is unlikely to be primarily due to a persistent afferent barrage from the peripheral region. Furthermore, in contrast to studies on various neuropathic pain conditions, fentanyl and S-ketamine in the present doses failed to attenuate AO pain.
authors.affiliation: Department of Clinical Oral Physiology, School of Dentistry, University of Aarhus, Vennelyst Boulevard 9, DK-8000 Aarhus C, Denmark. lbhansen@odont.au.dk
authors.forename: Lene
authors.initials: L
authors.lastname: Baad-Hansen
authors.forename: Gitte Irene
authors.initials: GI
authors.lastname: Juhl
authors.forename: Troels Staehelin
authors.initials: TS
authors.lastname: Jensen
authors.forename: Birgitte
authors.initials: B
authors.lastname: Brandsborg
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson
mesh_terms: D000328:Adult; D000700:Analgesics / Q000627:therapeutic use*; D000704:Analysis of Variance; D019540:Area Under Curve; D002211:Capsaicin; D016022:Case-Control Studies; D004311:Double-Blind Method; D004333:Drug Administration Routes; D004334:Drug Administration Schedule; D005260:Female; D005283:Fentanyl / Q000627:therapeutic use*; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy; D007649:Ketamine / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy* / Q000503:physiopathology; D010147:Pain Measurement; D014098:Toothache / Q000188:drug therapy* / Q000503:physiopathology
chemical_list: D000700:Analgesics; D007649:Ketamine; D002211:Capsaicin; D005283:Fentanyl