L-menthol as a Topical Counter-irritant to TRPA1-induced Neurogenic Inflammation and Pain

January 11, 2016 updated by: Parisa Gazerani, Aalborg University

High-concentration L-menthol as a Counter-irritant to TRPA1-induced Neurogenic Inflammation, Thermal and Mechanical Hyperalgesia Caused by Trans-cinnamaldehyde

The aim of this study is to quantitatively characterize the effects of L-menthol as a topical counter-irritant on cutaneous pain and hyperalgesia provoked by topical application of the TRPA1-agonist trans-cinnamaldehyde (CA) in healthy human volunteers.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

This study is designed as an experimental model in healthy humans.

Study Type

Interventional

Enrollment (Actual)

14

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

Yes

Description

Inclusion Criteria:

  • 18 healthy men and women aged 18-50 years willing to abstain from alcohol, nicotine, caffeine and pain medication 24 hours before experimental sessions

Exclusion Criteria:

  • Pregnancy
  • Skin disorders (e.g. contact eczema)
  • Chronic pain conditions
  • Drug addiction defined as the use of cannabis, opioids or other drugs
  • Previous neurologic, musculoskeletal or mental illnesses
  • Lack of ability to cooperate

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: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Placebo Comparator: Vehicle, topical ethanol 96%
Exposure: 10 % topical trans-cinnamaldehyde [CAS Number: 14371-10-9] Vehicle: 96% ethanol
Other: Vehicle, topical ethanol 96%
Organic solvent CAS Number: 64-17-5
Experimental: Topical L-menthol 40%
Exposure: 10 % trans-cinnamaldehyde [CAS Number: 14371-10-9] Intervention: 40% l-menthol [CAS Number: 2216-51-5] Vehicle: 96% ethanol
Other: Topical L-menthol 40%
Naturally occurring local anaesthetic, counterirritant and TPRM8-agonist. CAS Number: 2216-51-5
Other Names:
  • Menthol

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Spontaneous pain intensity [self-reported on a visual analog scale]
Time Frame: 0-20 minutes with a sampling frequency of 1/1 min
Rating of the overall pain intensity on a visual analog scale (VAS ranging from "No pain" = 0, to "worst imaginable pain" =10) once every minute
0-20 minutes with a sampling frequency of 1/1 min

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Neurogenic inflammation [Measured by Laser speckle flowmetry in a 3x3 cm area]
Time Frame: 20-25 minutes post induction
Speckle contrast flowmetry (MoorFLPI, Moor Instruments, Devon, UK). The assessment is conducted with a 30-cm distance between the head of the laser and the application area with an exposure time of 8.3ms. Single frame images are analyzed on appertaining software (MoorFLPI Review V 4.0, Moor Instruments), upon which the arithmetic mean flux (arbitrary units) is calculated. The longitudinal analysis of the spatial dispersion of neurogenic inflammation is performed using the line histogram tool. A 7-cm line centered in the area of application was placed longitudinally along the volar forearm and the perfusion intensity is recorded every 2.5 mm.
20-25 minutes post induction
Heat hyperalgesia
Time Frame: 25-27.5 minutes post induction
Heat pain threshold assessments is performed with a Medoc Pathway (Medoc Ltd, Ramat Yishay, Israel) equipped with a 3 × 3 cm advanced thermal stimulator probe where the baseline temperature was set to 32 °C. Ramp stimuli of 1 °C/s are delivered and the subjects are asked to identify the heat pain threshold upon which the temperature is returned to the baseline at a rate of 5 °C/s. The test result is calculated as the arithmetic mean of the outcome from three repeated stimuli. Heat hyperalgesia is considered to be a significant drop in heat pain threshold
25-27.5 minutes post induction
Mechanical hyperalgesia
Time Frame: 27.5-30 minutes post induction
To evaluate the mechanical pain threshold (MPT) an electronic von Frey transducer and an electronic coVAS connected to a SENSE-Box setup is used (both items: Somedic, Hörby, Sweden). Five ramp stimuli from 0-110 g at a rate of 5g/1 sec with the default stimulus probe is conducted at different locations within the application area. The subjects are instructed to continuously rate the perceived pain on the coVAS ranging from "No pain" (0) to "worst imaginable pain" (10). The arithmetic mean of the VAS scores yields three MPTs (fixed to VAS = 0.5, 1 and 2) and an area-under-the-curve (AUC).
27.5-30 minutes post induction

Collaborators and Investigators

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

Sponsor

Aalborg University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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

October 1, 2014

Primary Completion (Actual)

December 1, 2014

Study Completion (Actual)

December 1, 2014

Study Registration Dates

First Submitted

January 8, 2016

First Submitted That Met QC Criteria

January 11, 2016

First Posted (Estimate)

January 12, 2016

Study Record Updates

Last Update Posted (Estimate)

January 12, 2016

Last Update Submitted That Met QC Criteria

January 11, 2016

Last Verified

January 1, 2016

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • N-20130005

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

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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