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Capsaicin-induced Muscle Pain in Humans

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT02377180
Recruitment Status : Completed
First Posted : March 3, 2015
Last Update Posted : January 18, 2017
Aalborg University
Information provided by (Responsible Party):
University Hospital Inselspital, Berne

Brief Summary:

There is currently no specific diagnostic test for primary muscular pain. The present study investigates whether selective blockade of the suprascapular nerve can effectively abolish experimental pain arising from the supraspinatus muscle. Experimental muscle pain is induced by intramuscular injection of capsaicin, an alkaloid from red chili peppers. The study consists of three parts:

  1. to describe the development, time course and intensity of capsaicin-induced muscle pain
  2. to evaluate the effectiveness of suprascapular nerve block against capsaicin-induced muscle pain
  3. to compare suprascapular nerve block and direct intramuscular local anesthetic infiltration for their effectiveness in capsaicin-induced muscle pain

Condition or disease Intervention/treatment Phase
Healthy Procedure: Intramuscular capsaicin injection Procedure: Suprascapular nerve block Procedure: Local anesthetic infiltration Not Applicable

Detailed Description:


Musculoskeletal pain is one of the most common reasons for consulting a physician. Many musculoskeletal pain disorders are associated with a widespread decrease in pain thresholds, indicating a state of hyperexcitability of the central nervous system.

This central hypersensitivity can be assessed by measuring pain thresholds to different experimental stimuli, using so-called quantitative sensory tests (QST).

Several experimental pain models are being used in healthy volunteers in order to study the central mechanisms of pain processing. Injection of capsaicin is one of them, which is associated with spreading of local pain, development of referred pain and hyperalgesia to thermal, mechanical or electrical stimuli.

Intramuscular injection of capsaicin is therefore potentially interesting for investigating primary muscle pain, central hypersensitivity and endogenous pain modulation. The present research project comprises three substudies which use intramuscular capsaicin to detect changes in central pain processing and to evaluate clinical tools for the diagnosis of primary muscle pain.

Part 1: The investigators hypothesize that the intensity, duration and expansion area of capsaicin-induced muscle pain depends on a subject's endogenous pain modulation. The investigators expect that subjects with strong endogenous pain modulation develop less pain and hyperalgesia after capsaicin injection than subjects with poor endogenous pain modulation. A large sample of healthy volunteers will therefore be screened using QST and then recruited for capsaicin injection if they show either very strong or very weak endogenous pain modulation. The data of the whole sample can be used to determine normative values of endogenous pain modulation.

Part 2 investigates the ability of suprascapular nerve block to abolish primary muscle pain. Healthy volunteers will receive capsaicin injection into the supraspinatus muscle or the trapezius muscle as a control condition in a randomized, blinded fashion. The investigators expect that the nerve block is more effective in the former compared to the latter muscle.

Part 3 compares the analgesic efficacy of suprascapular nerve block and direct intramuscular local anesthetic infiltration of the supraspinatus muscle after capsaicin injection. This will determine which procedure is more effective to treat primary muscle pain.


  1. To determine normative values for endogenous pain modulation in healthy volunteers
  2. To demonstrate that capsaicin-induced pain and hyperalgesia depend on endogenous pain modulation
  3. To calculate sensitivity and specificity of suprascapular nerve block for the diagnosis of primary muscle pain
  4. To determine whether suprascapular nerve block or intramuscular local anesthetic infiltration are more effective against muscle pain


  1. intramuscular injection of capsaicin
  2. quantitative sensory tests (pressure pain thresholds)
  3. ultrasound-guided suprascapular nerve block
  4. ultrasound-guided intramuscular local anesthetic infiltration

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 72 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single (Participant)
Primary Purpose: Basic Science
Official Title: Capsaicin-induced Muscle Pain in Humans: From Investigating Central Pain Processing to Developing Clinical Applications
Study Start Date : September 2014
Actual Primary Completion Date : December 2016
Actual Study Completion Date : December 2016

Resource links provided by the National Library of Medicine

Drug Information available for: Capsaicin

Arm Intervention/treatment
Experimental: Part 1
Intramuscular injection of capsaicin for the study of pain and hyperalgesia
Procedure: Intramuscular capsaicin injection
Intramuscular injection of capsaicin: 50 mcg/0.5 ml

Active Comparator: Part 2
Pain arising from supraspinatus muscle vs. pain arising from trapezius muscle. Nerve block is only expected to be effective in the former.
Procedure: Suprascapular nerve block

Injection of capsaicin 50 mcg/0.5 ml into the supraspinatus or trapezius muscle in randomized order, followed by suprascapular nerve block (ultrasound-guided) using Lidocaine 1%; nerve block is expected to be effective only in pain arising from the supraspinatus muscle. Trapezius pain serves as control condition.

Evaluates the diagnostic validity of suprascapular nerve block for muscle pain.

Active Comparator: Part 3
Suprascapular nerve block vs. intramuscular local anesthetic against pain arising from the supraspinatus muscle.
Procedure: Local anesthetic infiltration
Injection of capsaicin 50 mcg/0.5 ml into the supraspinatus muscle in two different sessions; suprascapular nerve block in one session and intramuscular local anesthetic infiltration in one session (in randomized order) using Lidocaine 1%; the aim is to investigate which procedure provides faster and more efficient pain relief. Compares effectivity of suprascapular nerve block vs. intramuscular local anesthetic infiltration.

Primary Outcome Measures :
  1. Intensity of shoulder pain on numeric rating scale [ Time Frame: two hours ]

Secondary Outcome Measures :
  1. Pressure pain thresholds [ Time Frame: two hours ]
  2. Area of referred pain [ Time Frame: two hours ]

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 80 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Age 18-80 years
  • Written informed consent

Exclusion Criteria

  • Any acute pain at the moment of testing
  • Intake of analgesics 24hours before testing
  • Intake of antidepressants, anticonvulsants or benzodiazepines
  • Allergy to local anesthetic or skin disinfectant
  • Pregnancy or breast-feeding

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT02377180

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University Department of Anesthesiology and Pain Therapy,Inselspital Bern
Bern, Switzerland, 3010
Sponsors and Collaborators
University Hospital Inselspital, Berne
Aalborg University
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Study Chair: Michele Curatolo, M.D., Ph.D. Department of Anesthesiology and Pain Therapy, University of Washington, Seattle WA, USA
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Responsible Party: University Hospital Inselspital, Berne Identifier: NCT02377180    
Other Study ID Numbers: 066/13
First Posted: March 3, 2015    Key Record Dates
Last Update Posted: January 18, 2017
Last Verified: January 2017
Keywords provided by University Hospital Inselspital, Berne:
musculoskeletal pain
regional anesthesia
diagnostic nerve block
intramuscular capsaicin
referred pain
experimental pain
central hypersensitivity
human experimental pain
Additional relevant MeSH terms:
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Muscular Diseases
Musculoskeletal Diseases
Neuromuscular Diseases
Nervous System Diseases
Musculoskeletal Pain
Neurologic Manifestations
Anesthetics, Local
Central Nervous System Depressants
Physiological Effects of Drugs
Sensory System Agents
Peripheral Nervous System Agents
Dermatologic Agents