Hyperalgesia, Naloxone, Opioid Antagonist, Pain
Conditions
Keywords
secondary hyperalgesia, allodynia, mechanical pain threshold, naloxone, endogenous opioids, pain
Brief summary
Recent studies have focused on the role of endogenous opioids on central sensitization. Central sensitization is known to be impaired or altered in chronic pain conditions, as fibromyalgia or chronic tension headache. Animal studies have shown reinstatement of mechanical hypersensitivity following naloxone administration after resolution of an injury. This suggests latent sensitization. In the present study, investigators hypothesize that naloxone (2 mg/kg) can reinstate secondary hyperalgesia 168 hours after a first-degree burn-injury. Investigators aim therefore to show that latent sensitization is present in humans and is modulated by endogenous opioids.
Interventions
DRUGNaloxone (2 mg/kg)
DRUGPlacebo
Sponsors
Rigshospitalet, Denmark
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
QUADRUPLE (Subject, Caregiver, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
MALE
Age
20 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
* healthy man * written informed consent * ASA 1-2 * BMI 18 \< BMI \< 30 * normal ultrasound examination of the heart * normal ECG * urin sample without traces of opioids
Exclusion criteria
* volunteers, who do not understand the Danish language * participation in another experimental trial in the previous 60 days * nerve damage or skin lesions in the assessment areas * neurological or psychiatric condition * use of psycho-active drugs * abuse of alcohol or drugs * chronic pain * regular use of pain-killers (\> 1 a week) * allergy against morphine or other opioids (including naloxone) * use of prescription drugs 1 week prior to the trial * use of over-the-counter medication 48 hours prior to the trial * urin sample with traces of opioids * volunteer is not suitable for the trial according to the investigator's consideration
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Secondary hyperalgesia area (cm2) surrounding a first-degree burn injury before and after infusion of naloxone/placebo | 1h, 2h, 3h, 168h, 168h15min, 168h30min post-burn | Areas of secondary hyperalgesia surrounding a first degree burn-injury will be assessed before and after infusion of naloxone/placebo. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in allodynic area (cm2) surrounding a first-degree burn injury before and after infusion of naloxone/placebo | 1h, 2h, 3h, 168h, 168h15min, 168h30min post-burn | Areas of allodynia surrounding a first degree burn-injury will be assessed before and after infusion of naloxone/placebo. |
Other
| Measure | Time frame | Description |
|---|---|---|
| Change in Mechanical Pain Thresholds at primary hyperalgesia site before and after naloxone/placebo infusion | 0h, 168h, 168h30min | Mechanical Pain Thresholds will be assessed with pinprick stimulators at baseline and after infusion of naloxone/placebo at the primary hyperalgesia site (following a first degree burn) and in the contralateral leg. |
Countries
Denmark
Outcome results
None listed