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 previously unrecognized effects of opioids. Intradermal injection of capsaicin (injection of pepper extract into the skin) is an established pain model in humans. The investigators want to test the influence of remifentanil, an ultra-short acting opioid, on hyperalgesia observed after intradermal capsaicin in human volunteers in a double blind cross-over prospective active placebo controlled clinical trial.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
24
Remifentanil (Ultiva®; Glaxo-Smith-Kline; Vienna, Austria) will be applied intravenously during 60 minutes through a dedicated infusion pump (TCI Alaris PK Syringe Pump, Cardinal Health, Baesweiler, Germany), with a Target Controlled Infusion (following the integrated software algorithm by Minto), reaching the initial 18ng/ml plasma concentration in 180 seconds. This corresponds to circa 0.7 µg kg-1 min-1
Midazolam (Dormicum®; Roche; Vienna, Austria) will be applied intravenously as active placebo at a dose of 15 µg kg-1 min-1 over 5 minutes to mimic typical central nervous side effects of remifentanil
Department of Anaesthesia, Medical University of Vienna
Vienna, State of Vienna, Austria
RECRUITINGArea of pin prick hyperalgesia
Time frame: 0-6 hours
Pain immediately after injection
Time frame: 0-15 min
Stimulus-response (SR) function to a set of modified rigid von Frey filaments (8-512 mN)
Time frame: 0-6 hours
Heat pain threshold within the area of mechanical hyperalgesia
Time frame: 0-6 hours
Mechanical pain threshold within the area of pin prick hyperalgesia, area of dynamic allodynia to brush
Time frame: 0-6 hours
Adverse effects
Time frame: 30 and 59 min after infusion of study medication
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