Treatment of chronic pain is a major clinical challenge since chronic pain is frequent and leads to deterioration of quality of life. An injury or wound can lead to long term changes in the nervous system that make the skin more sensitive at and near the injury; this is termed hyperalgesia and occurs through long term depotentiation (LTP), i.e. a change in the synaptic interaction between neurons.

Opioids are the gold standard for the symptomatic therapy of moderate to severe pain. Now, in animal studies the investigators have discovered a previously unrecognized effect of opioids, the reversal of these long term changes.

Intradermal injection of capsaicin (injection of pepper extract into the skin) is an established pain model in humans. The investigators want to test the hypothesis, that remifentanil, an ultra-short acting opioid, can reverse the hyperalgesia observed after intradermal capsaicin in human volunteers in a double blind cross-over prospective active placebo controlled clinical trial.