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

Aalborg University20 enrolled

Overview

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 Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

SINGLE

Enrollment

Conditions

Itch

Interventions

Doxepin TopicalDRUG

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

PapainDRUG

Papain will be applied by 1 SPT prick thought the skin

HistamineDRUG

Histamine will be applied by 1 SPT prick thought the skin

Eligibility

Sex: ALLMin age: 18 YearsMax age: 60 YearsHealthy volunteers:

Medical Language ↔ Plain English

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)

Locations (1)

Aalborg University

Aalborg, North Denmark, Denmark

Outcomes

Primary Outcomes

Superficial blood perfusion

Superficial blood perfusion is measured by a Speckle contrast imager (FLPI, Moor Instruments, England).

Time frame: 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.

Time frame: 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".

Time frame: 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.

Time frame: 15 minutes

Secondary Outcomes

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.

Time frame: 15 minutes

Data from ClinicalTrials.gov

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