title: Intradermal capsaicin as a neuropathic pain model in patients with unilateral sciatica.
abstract: OBJECTIVE
  This study compared the responses between patients with unilateral sciatica and pain-free volunteers following administration of intradermal capsaicin. METHODS Fourteen patients with unilateral sciatica and 12 pain-free volunteers received one injection per hour over 4 h of 1 µg and 10 µg capsaicin, into each calf. For each dose, spontaneous pain (10 cm VAS), area of flare (cm²) and the sum of allodynia and hyperalgesia radii across eight axes (cm) were recorded pre-injection and at 5, 15, 30, 45 and 60 min post injection.
  
  
  RESULTS
  Sciatica subjects experienced higher spontaneous pain and hyperalgesia responses in both legs compared with pain-free volunteers. The largest mean difference in spontaneous pain was 2.8 cm (95% CI 1.6, 3.9) at 5 min in the unaffected leg following 10 µg. The largest mean difference in hyperalgesia was 19.7 cm (95% CI 12.4, 27.0) at 60 min in the unaffected leg following 10 µg. Allodynia was greater in patients than in controls with the largest mean difference of 2.9 cm (95% CI 1, 4.8) at 5 min following 10 µg in the affected leg. Allodynia was also higher in the affected leg compared with the unaffected leg in sciatica patients with the highest mean difference of 3.0 cm (95% CI 1.2, 4.7) at 5 min following 10 µg.
  
  
  CONCLUSIONS
  The responses to intradermal capsaicin are quantitatively and qualitatively different in unilateral sciatica patients compared with pain-free controls.
authors: Discipline of Pharmacology, University of Adelaide, Adelaide 5005, Australia.
authors: Verna
authors: V
authors: Aykanat
authors: Melanie
authors: M
authors: Gentgall
authors: Nancy
authors: N
authors: Briggs
authors: Desmond
authors: D
authors: Williams
authors: Sharon
authors: S
authors: Yap
authors: Paul
authors: P
authors: Rolan
mesh_terms: D000328:Adult; D002211:Capsaicin / Q000008:administration & dosage* / Q000494:pharmacology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy*; D007271:Injections, Intradermal / Q000379:methods; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D010146:Pain / Q000188:drug therapy*; D010147:Pain Measurement / Q000379:methods; D012585:Sciatica / Q000188:drug therapy*; D018689:Sensory System Agents / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D018689:Sensory System Agents; D002211:Capsaicin