title: The effect of wound instillation of a novel purified capsaicin formulation on postherniotomy pain: a double-blind, randomized, placebo-controlled study.
abstract: BACKGROUND
  Acute postoperative pain is common after most surgical procedures. Despite the availability of many analgesic options, postoperative pain management is often unsatisfactory. Purified capsaicin (ALGRX 4975 98% pure) has demonstrated prolong inhibition of C-fiber function in in vitro, preclinical, and clinical studies, and may be an effective adjunct to postoperative pain management.
  
  
  METHODS
  We performed a single-center, randomized, double-blind, placebo-controlled study of the analgesic efficacy of a single intraoperative wound instillation of 1000 microg ultrapurified capsaicin (ALGRX 4975) after open mesh groin hernia repair in 41 adult male patients. The primary end-point was average daily visual analog scale (VAS) pain scores during the first week after surgery assessed as area under the curve (AUC). Pain was recorded twice daily in a pain diary for 4 wk. Physical examination and laboratory tests were done before and 1 wk after surgery, together with recordings of adverse events up to 28 days. Adverse events were recorded. Data were also analyzed using a mixed-effects analysis with NONMEM.
  
  
  RESULTS
  VAS AUC was significantly lower during the first 3 days postoperatively (P < 0.05), but not for the whole 1 or 4 wk postoperatively. Mixed-effects analysis with NONMEM revealed that pain scores were significantly lower (P < 0.05) in the capsaicin group during the first 4 days. No clinically significant serious adverse events were observed, although a mild transient increase in liver enzymes was seen more often in the capsaicin-treated group.
  
  
  CONCLUSIONS
  In the setting of a well-defined analgesic protocol standard, VAS AUC analysis and a mixed-effect analysis showed superior analgesia of capsaicin relative to placebo during the first 3-4 days after inguinal hernia repair.
authors.affiliation: Section of Surgical Pathophysiology, the Juliane Marie Centre, Rigshospitalet, Copenhagen, Denmark. eskeaasvang@rh.hosp.dk
authors.forename: Eske K
authors.initials: EK
authors.lastname: Aasvang
authors.forename: Jeanette B
authors.initials: JB
authors.lastname: Hansen
authors.forename: Jørgen
authors.initials: J
authors.lastname: Malmstrøm
authors.forename: Torsten
authors.initials: T
authors.lastname: Asmussen
authors.forename: Daniel
authors.initials: D
authors.lastname: Gennevois
authors.forename: Michel M R F
authors.initials: MM
authors.lastname: Struys
authors.forename: Henrik
authors.initials: H
authors.lastname: Kehlet
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002211:Capsaicin / Q000008:administration & dosage* / Q000009:adverse effects; D004311:Double-Blind Method; D059685:Herniorrhaphy; D006801:Humans; D007322:Instillation, Drug; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy*
chemical_list: C528652:ALGRX-4975; D002211:Capsaicin