Pain Thresholds Under High-dose Topical Capsaicin

Study Overview
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Brief Summary
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Aim of the study is to determine heat pain thresholds (HPT in °C) and cold pain thresholds (CPT in °C) during topical capsaicin 8% application, and mechanical pain thresholds (MPT in g) immediately after to find out the exact skin temperature by which capsaicin initiates the application pain (heat pain threshold, HPT in °C) but also the temperature by which capsaicin does not yet trigger a cold pain (cold pain threshold, CPT in °C). Moreover the investigators want to find out the mechanical pain threshold in g from topical capsaicin and to verify a prolonged effect of capsaicin on the pain thresholds.

Detailed Description
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Capsaicin is the main pungent ingredient in chili peppers. Topical capsaicin 8% is used for the treatment of peripheral neuropathic pain. Application of capsaicin 8% provokes distinct pain by activating the transient receptor potential vanilloid 1 (TRPV1) receptor. Cooling the skin results in a reliable prevention of the application pain. However, the necessary cooling temperature and if cooling itself produces application pain, is unknown. Materials and Methods: 10 female and 10 male healthy volunteers will be enrolled in a randomised, double blind, placebo controlled, cross-over study. The left or right forearm of each subject is going to be treated with a capsaicin 8% patch (QUTENZA, Astellas Pharma, Tokyo, Japan) of 9 cm² or a placebo patch (Demo patch, Astellas Pharma, Tokyo, Japan) of the same size for 60 min. Then the other forearm (which has not been tested before) will be treated with the remaining patch. During capsaicin and placebo exposure HPT in °C and CPT in °C are going to be obtained by the thermode of a thermal sensory analyser, TSA-II (Medoc Ltd., Ramat Yishai, Israel). Temperature increase/decrease of the thermode will be stopped, as soon as the subject presses a switch because of a beginning pain sensation. Immediately after exposure a pin prick test will be performed 5 times in a row by pressing a Mini-Spike (B. Braun Melsungen AG, Melsungen, Germany) slowly against the skin of the application areal to determine the pressure necessary to provoke a sharp pain (Mechanical pain threshold in g). 2 weeks later HPT, CPT, and MPT will be determined again in the areas of capsaicin and placebo exhibition.

Official Title
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Heat-, Cold-, and Mechanical Pain Thresholds Under Exposition of High Dose Topical Capsaicin

Conditions
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Pain

Intervention / Treatment
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* Drug: Topical High dose Capsaicin
* Drug: Topical Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: healthy volunteers 18 ore more years old Exclusion Criteria: dermatologic or neurologic injuries on both thighs, (possible) pregnancy

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Capsaicin<br>Treatment with Topical High dose Capsaicin | Drug: Topical High dose Capsaicin<br>* Topical High dose Capsaicin exposure within an area of 3x3 cm for 60 minutes<br>* Other names: Qutenza® patch;|
| Placebo Comparator: Placebo<br>Treatment with Topical Placebo | Drug: Topical Placebo<br>* Placebo exposure within an area of 3x3 cm for 60 minutes<br>* Other names: Demo patch;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heat pain threshold (HPT) in degrees Celsius (°C) | During capsaicin and placebo exposure HPT in degrees Celsius (°C) is determined by a thermal sensory analyser TSA-II (Medoc Ltd.) | 60 minutes during topical highdose Capsaicin/Placebo exposure | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cold pain threshold (CPT) in degrees Celsius (°C) | During capsaicin and placebo exposure CPT in degrees Celsius (°C) is determined by a thermal sensory analyser TSA-II (Medoc Ltd.) | 60 minutes during topical highdose Capsaicin/Placebo exposure | 
| Mechanical pain threshold (MPT) in grams (g) | After capsaicin and placebo exposure MPT in grams (g) is determined by pressing a Mini-Spike (B. Braun Melsungen AG, Melsungen, Germany) slowly against the skin of the application areal to determine the pressure necessary to provoke a sharp pain | Immediately after topical highdose Capsaicin/Placebo exposure | 
| HPT in degrees Celsius (°C) | HPT in degrees Celsius (°C) will be determined again in the areas of capsaicin and placebo Exhibition | 2 weeks after exposure | 
| CPT in degrees Celsius (°C) | CPT in degrees Celsius (°C) will be determined again in the areas of capsaicin and placebo Exhibition | 2 weeks after exposure | 
| MPT in grams (g) | MPT in grams (g) will be determined again in the areas of capsaicin and placebo Exhibition | 2 weeks after exposure | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Heat pain threshold, Cold pain threshold, Mechanical pain threshold, High dose Capsaicin