A new human experimental pain model

THE heat/capsaicin sensitization model is a new human experimental pain model that synergistically combines non-invasive physical and chemical methods of nociceptor stimulation to produce stable and long-lasting hyperalgesia with a low potential for skin injury. In 10 healthy volunteers the forearm was stimulated with a 45°C thermode for 5 min to produce an area of secondary hyperalgesia. Applying capsaicin cream for 30 min further expanded the area of secondary hyperalgesia. Periodically heating the treated skin with a previously non-painful temperature of 40°C re-kindled the sensitization enough to maintain stable areas of secondary hyperalgesia for 4 h. The evoked pain was moderate and well tolerated. The heat/capsaicin sensitization model should be well suited for studying pain mechanisms and testing new analgesics.