Experimental interventions that activate specific components of clinical
pain are necessary for characterization of underlying mechanisms and pharmacology. Cutaneous
hyperalgesia has been described that uses nonpainful heat to induce secondary
hyperalgesia. This study evaluated the effect of intravenous
alfentanil on experimental cutaneous
hyperalgesia created using this method. Eighteen subjects participated in a randomized, double-blinded, placebo-controlled crossover study consisting of 2 sessions, 1 with
alfentanil and 1 with placebo. Using a computer-controlled
infusion pump,
alfentanil or matching placebo was maintained at a constant plasma level of 75 ng/mL for 1 hour followed by the application of a 40°C heat stimulus to the right thenar eminence for 15 minutes. The temperature was raised by 1°C every 15 minutes until the subject reported
pain or 45°C was reached. After the end point was reached, the temperature was maintained, and repeat testing was performed. The nonpainful heat created an area of secondary cutaneous
hyperalgesia and significant decrease in mechanical pain threshold on heat-treated right vs untreated left during placebo administration.
Alfentanil prevented the
hypersensitivity when compared to placebo (P < .05) but failed to reduce the area of secondary
hyperalgesia created by nonpainful heat when compared to placebo (P = .06). Neither
alfentanil nor the heat lamp treatment showed any significant effect on other neurosensory measures. This study demonstrated a reliable production of cutaneous
hyperalgesia using a nonpainful stimulus that is affected by the systemic delivery of
alfentanil. This model for human cutaneous experimental
pain may be a useful method for scientific characterization of
analgesics.