Clinical Trial: Capsaicin-induced Muscle Pain in Humans

Study Status: Completed
Recruit Status: Completed
Study Type: Interventional

Official Title: Capsaicin-induced Muscle Pain in Humans: From Investigating Central Pain Processing to Developing Clinical Applications

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

Detailed Summary:

Background

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
Sponsor: University Hospital Inselspital, Berne

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

Original Primary Outcome: Same as current

Current Secondary Outcome:

  • Pressure pain thresholds [ Time Frame: two hours ]
  • Area of referred pain [ Time Frame: two hours ]


Original Secondary Outcome: Same as current

Information By: University Hospital Inselspital, Berne

Dates:
Date Received: February 11, 2015
Date Started: September 2014
Date Completion:
Last Updated: January 16, 2017
Last Verified: January 2017