Can Fentanyl Lead to Opioid-induced Hyperalgesia in Healthy Volunteers?

The purpose of this study is to examine whether two clinically sensible dose regimen of fentanyl (low dose vs. high dose) lead to different pain scores as measured by the nonverbal rating scale (NRS) in healthy volunteers at 4.5 to 6.5 hours after fentanyl application. Pain modalities tested will include transdermal electrical stimulation and cold pressor pain. The investigators hypothesize that the high dose fentanyl group will have an increase of approximately 20% in the NRS.