Study on the Development of Opioid Induced Hyperalgesia (OIH) After Exposure to Alfentanil

Not Applicable

Completed

Brief Summary: The purpose of this study was to follow a person's response to experimental pain after multiple consecutive exposures to alfentanil or diphenhydramine to see if the person can tolerate the pain more, less, or the same at the end of the study.

Detailed Description: This project investigates the phenomenon of opioid-induced hyperalgesia (OIH). Opioid analgesics, in addition to their therapeutic anti-nociceptive effects, under some conditions produce pro-nociceptive effects. This phenomenon of pain or pain sensitivity being increased by prior opioid administration is called opioid-induced hyperalgesia. It is thought to be relevant both to pain management complications and to complications of opioid dependence and its treatment. This study investigated the time-course of opioid-induced hyperalgesia development in healthy normal volunteers (N=12 completers), using a series of acute alfentanil administrations (15 mg/kg mg intramuscular (IM) per day) spaced at 3-4 day intervals, with testing for pain tolerance using the cold pressor test (CPT), and mechanical quantitative sensory testing (MQST) each administered repeatedly over time within each testing day. The goal was to determine the time course of OIH development following acute opioid administration, and to assess whether this changes over repeated acute opioid administrations.

Recruitment & Eligibility

Inclusion Criteria

Exclusion Criteria

Lifetime substance use disorder, except for alcohol abuse/dependence in remission
Use of opiates in last 3 months
Ongoing marijuana use
Acute or chronic pain
Neurologic or psychiatric condition known to influence cold pressor testing (peripheral neuropathy, major depression, or schizophrenia)
Current use of prescribed or over the counter pain medications
Previous adverse reaction to opiate medications or diphenhydramine
Use of tobacco or caffeine on study days

Arm && Interventions

Group	Intervention	Description
Alfentanil	Alfentanil	Subjects received a series of acute alfentanil administrations each session (15 mcg/kg IM per session), with sessions spaced at 3-4 day intervals.
Diphenhydramine	Diphenhydramine	Subjects received a series of acute diphenhydramine administrations each session (25 mg IM per session), with sessions spaced at 3-4 day intervals.

Primary Outcome Measures

Name	Time	Method
Pain Tolerance	8 sessions over 4-6 weeks	The participant places their hand in a water bath kept at 4 degrees Celsius (cold pressor test). They then continue to hold the hand in the water bath until they can no longer tolerate the pain (pain tolerance) or until the end of the testing (truncated at 300 seconds for safety purposes). Reported as the mean (time to hand removal in seconds) at the 30 minute time point.

Secondary Outcome Measures

Name	Time	Method
Pain Threshold	8 sessions over 4-6 weeks	The amount of time (in seconds) before the participant first verbally reports feeling pain after placing hand in 4 degree Celsius circulating water bath at the 30 minute time point. Truncated at 300 seconds for safety purposes.