title: NGX-4010, a high-concentration capsaicin patch, for the treatment of postherpetic neuralgia: a randomised, double-blind study.
abstract: BACKGROUND
  The limitations of current treatments for postherpetic neuralgia (PHN) have led to the investigation of localised, non-systemic alternatives. NGX-4010, a high-concentration (8%) capsaicin dermal patch, was developed to treat patients with neuropathic pain. We report the results of a randomised, double blind, 12-week study of the efficacy and safety of one application of NGX-4010 in patients with PHN.
  
  
  METHODS
  In this multicentre, double-blind, parallel-group trial, 402 patients were randomly assigned to one 60-min application of NGX-4010 (640 microg/cm(2) [8% capsaicin]) or a low-concentration capsaicin control patch (3.2 microg/cm(2) [0.04% capsaicin]). Patients were aged 18-90 years, had had postherpetic neuralgia for at least 6 months, and had an average baseline numeric pain rating scale (NPRS) score of 3 to 9. The primary efficacy endpoint was percentage change in NPRS score from baseline to weeks two to eight. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00115310.
  
  
  RESULTS
  Patients who were randomly assigned to NGX-4010 (n=206) had a significantly greater reduction in pain during weeks two to eight than did patients who had the control patch (n=196). The mean changes in NPRS score were -29.6%vs -19.9% (difference -9.7%, 95% CI -15.47 to -3.95; p=0.001). 87 (42%) patients who received NGX-4010 and 63 (32%) controls had a 30% or greater reduction in mean NPRS score (odds ratio [OR] 1.56, 95% CI 1.03 to 2.37; p=0.03). The patients who had NGX-4010 had significant improvements in pain during weeks two to 12 (mean change in NPRS score -29.9%vs -20.4%, difference -9.5, -15.39 to -3.61; p=0.002). Transient blood pressure changes associated with changes in pain level were recorded on the day of treatment, and short-lasting erythema and pain at the site of application were common, self-limited, and generally mild to moderate in the NGX-4010 group and less frequent and severe in the controls.
  
  
  CONCLUSIONS
  One 60-min application of NGX-4010 provided rapid and sustained pain relief in patients with postherpetic neuralgia. No adverse events were associated with treatment except for local reactions at the site of application and those related to treatment-associated pain.
authors.affiliation: University of Wisconsin-Madison, Madison, WI 53792, USA. backonja@neurology.wisc.edu
authors.forename: Miroslav
authors.initials: M
authors.lastname: Backonja
authors.forename: Mark S
authors.initials: MS
authors.lastname: Wallace
authors.forename: E Richard
authors.initials: ER
authors.lastname: Blonsky
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Cutler
authors.forename: Philip
authors.initials: P
authors.lastname: Malan
authors.forename: Richard
authors.initials: R
authors.lastname: Rauck
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Tobias
mesh_terms: D000279:Administration, Cutaneous; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002211:Capsaicin / Q000008:administration & dosage* / Q000009:adverse effects / Q000031:analogs & derivatives*; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004890:Erythema / Q000139:chemically induced; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051474:Neuralgia, Postherpetic / Q000188:drug therapy* / Q000503:physiopathology; D010146:Pain / Q000139:chemically induced; D010147:Pain Measurement; D018689:Sensory System Agents / Q000008:administration & dosage* / Q000009:adverse effects; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D018689:Sensory System Agents; D002211:Capsaicin