Characterization of New Human Models of Non-histaminergic Itch and Their Interaction With the TRPM8 Receptor

In this experiment the investigators would like to assess if papain induces an itch sensation comparable to the itch sensation induced by cowhage and to confirm that the mechanism of action of papain follows the non-histaminergic pathway.

Study Overview

• Status: Completed
• Conditions: Itch
• Intervention / Treatment: Drug: Doxepin Topical; Drug: Papain; Drug: Histamine; Other: Cowhage

• Study Type: Interventional
• Enrollment (Actual): 20
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Denmark
  • Nordjylland
    • Aalborg, Nordjylland, Denmark, 9000
      • Aalborg University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 16 years to 58 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Healthy men and women
• 18-60 years
• Speak and understand English

Exclusion Criteria:

• Pregnancy or lactation
• Drug addiction defined as any use of cannabis, opioids or other addictive drugs
• Previous or current history of neurological, dermatological, immunological musculoskeletal, cardiac disorder or mental illnesses that may affect the results (e.g. neuropathy, muscular pain in the upper extremities, etc.).
• Lack of ability to cooperate
• Current use of medications that may affect the trial such as antihistamines, antipsychotics and pain killers, as well as systemic or topical steroids.
• Skin diseases
• Moles, scars or tattoos in the area to be treated or tested.
• Hypersensitivity to papaya and mango fruit, cashew nuts, rubber latex
• Consumption of alcohol or painkillers 24 hours before the study days and between these
• Acute or chronic pain
• Participation in other trials within 1 week of study entry (4 weeks in the case of pharmaceutical trials)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Doxepin Application; During the session each forearm of the subject will be divided into four squared areas (2.5x2.5 cm), see Figure 4. Four of the areas will be treated with doxepin for 1 hour and 30 minutes (with a patch to deposit 1.2 grams of cream). Each patch will be covered with Tegaderm I.V., an occlusive, adhesive dressing (3M), for at least 1½ hours 48. At the end of the pre-treatment period, the patches will be removed and the skin will be cleaned with alcohol.	Drug: Doxepin Topical; Four of the areas will be treated with doxepin for 1 hour and 30 minutes (with a patch to deposit 1.2 grams of cream). Each patch will be covered with Tegaderm I.V., an occlusive, adhesive dressing (3M), for at least 1½ hours
Experimental: Itch Induction; After Doxepin removal, Then tests with papain, cowhage, histamine or vehicle will be conducted. Each substance will be randomly applied in two areas, one pretreated with doxepin and one with no pre-treatment.	Drug: Papain; Papain will be applied by 1 SPT prick thought the skin; Drug: Histamine; Histamine will be applied by 1 SPT prick thought the skin; Other: Cowhage; Cowhage spicules are 1-2 mm in length and have diameter of 1-3 µm at their tip. 30-35 spicules are gently rubbed into a 1 cm diameter skin area.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Superficial blood perfusion	Superficial blood perfusion is measured by a Speckle contrast imager (FLPI, Moor Instruments, England).	15 minutes
Measuring itch intensity by computerized Visual Analog Scale Scoring	The subjects will rate the sensation of itch on a 100 mm VAS scale ranging from 0 to 100 where 0 indicates "no itch" and 100 indicates "worst itch imaginable" and similarly for sensations of stinging/pricking and burning, both of which are frequently associated with the sensation of itch.	15 minutes
Measuring pain intensity by computerized Visual Analog Scale Scoring	The subjects will rate the sensation of pain on a 100 mm VAS scale ranging from 0 to 100 where 0 indicates "no pain" and 100 indicates "worst pain imaginable".	15 minutes
Measuring Alloknesis	Alloknesis is measured by using mildly pruritic, non-painful von Frey nylon filaments of a predetermined intensity (generally 5-30 milliNewton of force). This stimulator is applied 0.5 cm outside the area of itch provocation.	15 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Measurement of Cold Detection Thresholds (CDT)	The tests for thermal sensation will all be conducted using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. During the first 8 seconds, the temperature decreases 1°C per second from a starting temperature of 32°C until the subject perceives a temperature change (cold sensation) and presses a button that will terminate the measurement and return the temperature to baseline at a rate of 5°C /s. A cut-off temperature of 0°C will be used.	15 minutes
Measurement of Cold PainThresholds (CPT)	The tests for thermal sensation will all be conducted using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. During the first 8 seconds, the temperature decreases 1°C per second from a starting temperature of 32°C until the subject perceives a temperature change (cold sensation) and presses a button that will terminate the measurement and return the temperature to baseline at a rate of 5°C /s. A cut-off temperature of 0°C will be used.	15 minutes
Measurement of Heat Pain Thresholds (HPT)	The tests for thermal sensation will all be performed using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. During the first 8 seconds, the temperature raises 1°C per second from a starting temperature of 32°C until the subject detects a painful sensation and presses a button that will terminate the measurement and return the temperature to baseline at a rate of 5°C /s. A cut-off temperature of 52°C will be used.	15 minutes
Measurement of Warm Detection Thresholds (WDT)	The tests for thermal sensation will all be performed using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. During the first 8 seconds, the temperature raises 1°C per second from a starting temperature of 32°C until the subject detects a painful sensation and presses a button that will terminate the measurement and return the temperature to baseline at a rate of 5°C /s. A cut-off temperature of 52°C will be used.	15 minutes
Measurement of Pain to Supra-threshold Heat Stimuli	The tests will be conducted by using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. The subjects will have to rate the pain to two suprathreshold heat pain stimuli (starting and ending at 32°C with an increase and decrease of 5°C and 3 s plateau at 50°C).	15 minutes
Measurement of Mechanical Pain Thresholds (MPT)	This test is conducted using a pin-prick set (Aalborg University, Aalborg). This test is conducted using a pin-prick set (Aalborg University, Aalborg).easurement of Mechanical Pain Thresholds (MPT)	15 minutes
Measurement of Mechanical Pain Sensitivity (MPS)	This test is conducted using a pin-prick set (Aalborg University, Aalborg).	15 minutes
Touch Pleasantness (TP)	Pleasant touch sensation measured using astandardized sensory brush (SENSELab Brush-05, Somedic AB, Hörby, Sweden) exerting a force of 200 to 400 mN.	15 minutes

Collaborators and Investigators

• Sponsor: Aalborg University

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2022
• Primary Completion (Actual): May 31, 2022
• Study Completion (Actual): June 30, 2022

Study Registration Dates

• First Submitted: September 14, 2020
• First Submitted That Met QC Criteria: September 14, 2020
• First Posted (Actual): September 18, 2020

Study Record Updates

• Last Update Posted (Actual): July 20, 2022
• Last Update Submitted That Met QC Criteria: July 19, 2022
• Last Verified: July 1, 2022

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Central Nervous System Depressants; Psychotropic Drugs; Antidepressive Agents; Hypnotics and Sedatives; Antidepressive Agents, Tricyclic; Sleep Aids, Pharmaceutical; Histamine Antagonists; Histamine Agents; Histamine Agonists; Doxepin; Histamine
• Other Study ID Numbers: N-20200005 2nd project

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No