title: Characterization of a reproducible gastric pain model using oral capsaicin titration in healthy volunteers.
abstract: BACKGROUND
  Sensory sensitization is one of the main pathophysiological hypotheses in functional gastrointestinal disorders (FGIDs). As sensitization may affect various sensory modalities, we aimed to develop a reproducible gastric pain model utilizing polymodal pathways for use in functional and other pain disorders.
  
  
  METHODS
  In this double-blind, cross-over study 42 healthy subjects swallowed one capsule containing either capsaicin 0.5mg or nocebo every 15min until moderate pain (intensity >30 on 100mm visual analogue scale) was attained for at least 5min. Pain was rated every minute. Capsaicin titration was repeated thrice for reliability calculation.
  
  
  RESULTS
  Moderate pain in the upper abdomen was successfully achieved in 38 of 42 subjects (90%) with capsaicin titration and in one of 42 (2%) with nocebo. The median dosage required to induce moderate pain for at least 5min was two capsules (interquartile range 1-3) and the median gastric pain intensity was 47 (41-53). The median duration of moderate pain was 8min (5-12). Moderate pain was successfully reproduced with capsaicin in all subjects on study days 2 and 3, with an excellent Cronbach reliability coefficient of >0.8.
  
  
  CONCLUSIONS
  Standardized gastric pain can be conveniently achieved in a majority of healthy subjects using a simple oral capsaicin titration, with minimal adverse events. The between-test reproducibility is high and nocebo responses are negligible. This technique stimulating a multimodal physiological pathway will be useful in the investigation of sensory changes in FGIDs, including functional dyspepsia.
authors.affiliation: Department of Medicine, National University of Singapore, Singapore.
authors.forename: Y
authors.initials: Y
authors.lastname: Cao
authors.forename: C H
authors.initials: CH
authors.lastname: Wilder-Smith
authors.forename: X H
authors.initials: XH
authors.lastname: Li
authors.forename: R K M
authors.initials: RK
authors.lastname: Wong
authors.forename: J
authors.initials: J
authors.lastname: Hammer
authors.forename: K Y
authors.initials: KY
authors.lastname: Ho
mesh_terms: D015746:Abdominal Pain / Q000139:chemically induced* / Q000503:physiopathology*; D000284:Administration, Oral; D000328:Adult; D002211:Capsaicin / Q000008:administration & dosage / Q000009:adverse effects*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005767:Gastrointestinal Diseases / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D010147:Pain Measurement; D011446:Prospective Studies; D015203:Reproducibility of Results; D018689:Sensory System Agents / Q000008:administration & dosage / Q000009:adverse effects; D013270:Stomach / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D018689:Sensory System Agents; D002211:Capsaicin