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.

Inclusion Criteria:

• Healthy (ASA I-II) male volunteers
• Age > 18 years
• BMI 18 - 25 kg/m2

Exclusion Criteria:

• Volunteers unable to give written informed consent
• Known drug allergies or intolerance to fentanyl
• Known drug allergies or intolerance to morphine and other opiates
• Recreational drug addiction or abuse
• Opiate use in the last month
• Volunteers taking confounding medication (analgesics, antihistamines, calcium or potassium channel blockers) in the last month
• History of motion sickness, neuropathy, chronic pain, neuromuscular or psychiatric disease
• Patients with renal failure (clearance < 30 ml/min)
• obstructive sleep apnea syndrome (OSAS)
• Indication for Rapid Sequence Induction
• Patients not understanding German, French, Italian or English