Role of the Endogenous Opioid System Underlying Modulation of Experimental Pain

July 11, 2012 updated by: University of Florida

Opioid Modulation of Two Models of Pain Inhibition in Healthy Controls and Patients With Temporomandibular Disorder (TMD)

The aim of this proposal is to characterize pain inhibition in healthy controls and Temporomandibular Disorder (TMD) patients with two models of endogenous pain modulation (off-set analgesia; conditioned pain modulation), and to investigate the function of the endogenous opioid system in these responses by using pharmacological blockade of the opioid receptor.

Study Overview

Status

Withdrawn

Conditions

Intervention / Treatment

Detailed Description

Dysfunction in endogenous pain inhibitory systems has been proposed as a factor in the development and maintenance clinical pain disorders particularly in Temporomandibular Disorder (TMD). Dysfunction has been observed with a model known as diffuse noxious inhibitory controls (DNIC), but other models that engage inhibitory systems (offset analgesia) have not been fully evaluated in chronic pain patients.

DNIC evaluates an individual's capacity to engage endogenous pain inhibition. The paradigm is a spatial inhibition model based on the principle that "pain-inhibits-pain" in which pain in a local area is inhibited by a second pain that can be anywhere else in the body. DNIC is traditionally studied by observing a reduction of pain produced by a focal pain stimulus (contact heat) as a result of a second painful stimulus. Research from our lab and others suggests that pain inhibition is reduced in a number of chronic pain conditions. The investigators preliminary data suggests that pain inhibition during DNIC is modulated in part by endogenous opioids; however, results from other DNIC studies have been mixed. In addition, it is possible that reductions in the ability to engage endogenous inhibitory systems in chronic pain patients are due to a weakening of the endogenous opioid system. While pharmacological studies have been conducted with healthy cohorts, only one study has examined the opioid involvement in chronic pain patients.

Offset analgesia is thought to reflect a form of temporal pain inhibition which is usually defined by three stimulus temperature phases: a baseline phase followed by a manipulation phase in which the temperature is briefly increased and returns to the baseline temperature during an "offset" phase. A reduction in pain ratings is observed approximately 15s after the temperature drop (third phase), which is ~50% lower than ratings at the same time point for "constant" trials that continued 48°C for 40s. No studies have examined offset analgesia in a chronic pain cohort or its sensitivity of opioid blockade.

Study Type

Interventional

Phase

  • Not Applicable

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 50 years (Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • ages 18-50 years old
  • Controls: pain-free based on Research Diagnostic Criteria (RDC) exam
  • TMD: chronic musculoskeletal pain (face) based on Research Diagnostic Criteria (RDC) exam

Exclusion Criteria:

  • Inability to adequately communicate and understand informed consent form;
  • Inability to reliably rate pain intensity;
  • Uncontrolled hypertension (or receiving treatment for hypertension with BP of greater than 140/95);
  • Serious systemic (e.g. Diabetes, thyroid problems, etc.);
  • Serious cardiovascular/pulmonary disease;
  • Neurological problems with significant changes in somatosensory and pain perception at the intended stimulation sites (hand, foot);
  • Serious psychiatric problems requiring treatment (schizophrenia, bipolar disorder);
  • Other chronic pain conditions (e.g., low back pain, fibromyalgia);
  • Any other ongoing acute pain problem (arthritis, injury-related pain); or,
  • Irregular menstrual cycles (>40 days) or menstrual cycle disorders (e.g. PMS, dysmenorrhea).

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: TMD patients

Intervention:

  • Drug: Naltrexone
  • Drug: placebo
Drug: Naltrexone
Oral, 50 mg, 1 Time Dose
Other Names:
  • Revia
Drug: Placebo
Oral, 1 Time Dose
Other Names:
  • Placebo/sugar pill
Active Comparator: Healthy controls

Intervention:

  • Drug: Naltrexone
  • Drug: placebo
Drug: Naltrexone
Oral, 50 mg, 1 Time Dose
Other Names:
  • Revia
Drug: Placebo
Oral, 1 Time Dose
Other Names:
  • Placebo/sugar pill

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Post-drug efficacy of pain inhibition
Time Frame: 1 hour after study medication (day 1)
A change in the ability to reduce experimental pain sensitivity during two models of pain inhibition will be evaluated before and after medication.
1 hour after study medication (day 1)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Florida

Collaborators

American Pain Society

Investigators

  • Principal Investigator: Christopher D King, PhD, University of Florida

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

December 1, 2011

Primary Completion (Actual)

July 1, 2012

Study Completion (Actual)

July 1, 2012

Study Registration Dates

First Submitted

March 24, 2011

First Submitted That Met QC Criteria

March 31, 2011

First Posted (Estimate)

April 1, 2011

Study Record Updates

Last Update Posted (Estimate)

July 13, 2012

Last Update Submitted That Met QC Criteria

July 11, 2012

Last Verified

July 1, 2012

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • APS2011

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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