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Completed

NCT Number: NCT04515056

Characterization of New Human Models of Non-histaminergic Itch

In this experiment the investigators would like to test a new new human itch model based on papain, and to characterize the sensory quality and temporary aspects of papain skin prick test (SPT) in comparison to the inactivated-cowhage delivery system.

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Key information

Conditions

Papain Itch Pathological Conditions, Signs and Symptoms Pruritus Signs and Symptoms Skin Diseases Skin Manifestations Skin Prick Test (SPT) Skin and Connective Tissue Diseases

Age range

18 year–60 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Aalborg University

Aalborg, North Denmark, 9000, Denmark

About this study

The most used model of non-histaminergic itch is cowhage but this models presents several problems, such us the impossibility of standardizing the amount of the spicules inserted in the skin and the difficulty of obtaining the substance. These aspects bring us the necessity to find a new and more standardized model of non-histaminergic itch.

Papain is a cysteine protease extracted from papaya plant that is known to cause itch if applied to the skin. For these reasons the investigators would like to test a new new human itch model based on papain, and to characterize the sensory quality and temporary aspects of papain skin prick test (SPT) in comparison to the inactivated-cowhage delivery system.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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)

Treatment and study plan

Papain 10 µg

Drug

The area will be exposed to 10 µg of papain.

Papain 50 µg

Drug

The area will be exposed to 50 µg of papain.

Papain 100 µg

Drug

The area will be exposed to 100 µg of papain.

Vehicle

Other

The area will be exposed to vehicle

Papain 1 SPT

Drug

Papain will be applied by 1 SPT prick thought the skin

Papain 5 SPT

Drug

Papain will be applied by 5 SPT pricks thought the skin

Papain 25 SPT

Drug

Papain will be applied by 25 SPT pricks thought the skin

Cowhage

Other

The last area will be exposed to cowage spicules (made chemically inert by autoclaving) soaked in 5 mg/ml papain solution.

Primary outcomes

  1. Superficial blood perfusion

    Time frame: 15 minutes

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

  2. Measuring itch intensity by computerized Visual Analog Scale Scoring

    Time frame: 15 minutes

    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.

  3. Measuring pain intensity by computerized Visual Analog Scale Scoring

    Time frame: 15 minutes

    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".

  4. Measuring Alloknesis

    Time frame: 15 minutes

    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.

Secondary outcomes

  1. Measurement of Cold Detection Thresholds (CDT)

    Time frame: 15 minutes

    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.

  2. Measurement of Cold Pain Thresholds (CPT)

    Time frame: 15 minutes

    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.

  3. Measurement of Warm Detection Thresholds (WDT)

    Time frame: 15 minutes

    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.

  4. Measurement of Heat Pain Thresholds (HPT)

    Time frame: 15 minutes

    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.

  5. Measurement of Pain to Supra-threshold Heat Stimuli

    Time frame: 15 minutes

    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).

  6. Measurement of Mechanical Pain Thresholds (MPT)

    Time frame: 15 minutes

    This test is conducted using a pin-prick set (Aalborg University, Aalborg).

  7. Measurement of Mechanical Pain Sensitivity (MPS)

    Time frame: 15 minutes

    This test is conducted using a pin-prick set (Aalborg University, Aalborg).

  8. Touch Pleasantness (TP)

    Time frame: 15 minutes

    Pleasant touch sensation measured using a standardized sensory brush (SENSELab Brush-05, Somedic AB, Hörby, Sweden) exerting a force of 200 to 400 mN.

Sponsors and collaborators

Lead sponsor

Aalborg University

Other

Registry information

Official study title

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

Important dates

Study start
2020
Primary completion
2021
Study completion
2021
First posted
Aug 17, 2020
Registry last updated
Jul 9, 2021

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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