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

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ClinicalTrials.gov Identifier: NCT02653703
Recruitment Status : Completed
First Posted : January 12, 2016
Last Update Posted : January 12, 2016
Information provided by (Responsible Party):
Parisa Gazerani, Aalborg University

Brief Summary:
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.

Condition or disease Intervention/treatment Phase
Inflammation Pruritus Hyperalgesia Other: Topical L-menthol 40% Other: Vehicle, topical ethanol 96% Not Applicable

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

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 14 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary Purpose: Basic Science
Official Title: High-concentration L-menthol as a Counter-irritant to TRPA1-induced Neurogenic Inflammation, Thermal and Mechanical Hyperalgesia Caused by Trans-cinnamaldehyde
Study Start Date : October 2014
Actual Primary Completion Date : December 2014
Actual Study Completion Date : December 2014

Resource links provided by the National Library of Medicine

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 Name: Menthol

Primary Outcome Measures :
  1. 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

Secondary Outcome Measures :
  1. 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.

  2. 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

  3. 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).

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Accepts Healthy Volunteers:   Yes

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

Publications automatically indexed to this study by ClinicalTrials.gov Identifier (NCT Number):
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Responsible Party: Parisa Gazerani, Professor, PharmD, Ph.D., Aalborg University
ClinicalTrials.gov Identifier: NCT02653703    
Other Study ID Numbers: N-20130005
First Posted: January 12, 2016    Key Record Dates
Last Update Posted: January 12, 2016
Last Verified: January 2016
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: Undecided
Additional relevant MeSH terms:
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Neurogenic Inflammation
Pathologic Processes
Skin Diseases
Skin Manifestations
Somatosensory Disorders
Sensation Disorders
Neurologic Manifestations
Nervous System Diseases
Anti-Infective Agents, Local
Anti-Infective Agents
Central Nervous System Depressants
Physiological Effects of Drugs
Dermatologic Agents