Table 2.

Capsaicin induced visceral hyperalgesia

Capsaicin Formulation	Method	Results	Reference
100 μg of capsaicin was dissolved in 1 ml of liquid and was given in volumes of 1, 2, 3… 10 ml.	Capsaicin was applied topically to the mucosa 5 cm in the gut by a plastic catheter via the stomal opening in patients with ileo- or colostomy.	Capsaicin evoked pain and referred pain areas in all subjects. Moreover, sympathetic manifestations were quantified by significant increases in the blood flow and temperature of the referred area.	Arendt-Nielsen et al. (2008)
180 ml acid (HCL, 0.1 M) and 2 mg capsaicin in 20 ml of solvent (10 ml/min).	Distal esophageal chemical perfusion (7 cm above lower esophageal sphincter).	Rectal hyperalgesia to heat and mechanical stimulations were demonstrated after chemical perfusion of the esophagus.	Brock et al. (2010)
Increasing volumes of capsaicin 50 μg/ml (0.25–3 ml)	Capsaicin was applied to the ileum via the stomal opening.	Hyperalgesia was found to cause distension of the gut after capsaicin application.	Drewes et al. (2003)
2.5 ml Tabasco capsaicin-containing red pepper sauce suspension.	Intraesophageal application of a capsaicin solution (10 cm above the lower esophageal sphincter).	Decreased perception and discomfort threshold of intraesophageal balloon distension.	Gonzalez et al. (1998)
180 ml of acid (HCL, 0.1 M) and 2 mg of capsaicin in 20 ml of solvent (10 ml/min).	Intraesophageal perfusion (7 cm above lower esophageal sphincter).	Results from evoked brain potentials following painful electrical stimulation of the rectosigmoid colon demonstrated visceral hypersensitivity as increased EEG power in the delta, theta, and alpha frequency bands were found.	Graversen et al. (2011)
Capsaicin (200 μg/ml, 2.5 ml/min). Duration of perfusion was 60 min or until discomfort.	Intraluminal capsaicin in different regions of the upper gastrointestinal tract.	In the duodenum, barostat volumes at sensation and discomfort were comparable before and after capsaicin perfusion, whereas in the jejunum balloon volumes were lower after capsaicin infusion.	Hammer and Vogelsang (2007)
Pretreatment: capsules (0.5 mg capsaicin) three times per day for 7 days.	Before and after capsule ingestion, the jejunum was distended with a balloon and perfused with a capsaicin solution.	Distension with 40 ml induced lower perception scores after 1 week of capsaicin treatment (desensitization). During capsaicin perfusion, discomfort thresholds were reported earlier after 1 week of capsaicin treatment (sensitization).	Hammer (2006)
Capsaicin perfusion: 40 μg/ml (infusion rate of 2.5 ml/min). Duration of perfusion was 60 min or until discomfort.
3 ml of a 0.17 mg/ml capsaicin solution, diluted with saline to a total volume of 10 ml	Intraesophageal capsaicin installation	No differences in symptom pattern or intensities induced by esophageal acid perfusion were found and neither was sensitivity to esophageal balloon distention.	Kindt et al. (2009)
0.84 mg capsaicin in 5 ml Tabasco capsaicin-containing red pepper sauce (10 ml/min.)	Capsaicin was applied in the gastric fundus.	After capsaicin perfusion, higher perception scores were reached for the same distending pressures by gastric barostat.	Lee et al. (2004)
180 ml of acid (HCL, 0.1 M) and 2 mg capsaicin in 20 ml of solvent (10 ml/min).	Distal esophageal chemical perfusion (7 cm above lower esophageal sphincter).	Reduction of the pain threshold to esophageal heat and electrical stimuli. Increase of the referred pain areas to esophageal mechanical and electrical stimulation.	Olesen et al. (2009)
Capsaicin solutions (40, 200, and 400 μg /ml) 2.5 ml/min were perfused for 60 min or until severe discomfort occurred.	Perfusion site at the ligament of Treitz and, 7 cm distally, a barostat balloon.	Repeated capsaicin (200 μg/ml) applications reduced time until discomfort occurred. Pain thresholds during distensions were not different before and after capsaicin perfusion.	Schmidt et al. (2004)