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Characterization of New Human Models of Non-histaminergic Itch

A

Aalborg University

Status

Completed

Conditions

Itch
Skin Prick Test (SPT)
Papain

Treatments

Drug: Papain 5 SPT
Drug: Papain 1 SPT
Drug: Papain 100 µg
Drug: Papain 50 µg
Other: Cowhage
Other: Vehicle
Drug: Papain 25 SPT
Drug: Papain 10 µg

Study type

Interventional

Funder types

Other

Identifiers

NCT04515056
N-20200005

Details and patient eligibility

About

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.

Full description

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.

Enrollment

20 patients

Sex

All

Ages

18 to 60 years old

Volunteers

Accepts Healthy Volunteers

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)

Trial design

Primary purpose

Basic Science

Allocation

Randomized

Interventional model

Single Group Assignment

Masking

Single Blind

20 participants in 2 patient groups

Papain dosage
Experimental group
Description:
In the 1st session, each of the middle forearms of the subject will be divided into two squared areas (4x4 cm). The two areas will be located 4 cm apart. Three areas will be exposed to 10, 50 or 100 µg of papain, while the last area will be used as control (exposed to a vehicle).
Treatment:
Drug: Papain 50 µg
Drug: Papain 10 µg
Drug: Papain 100 µg
Other: Vehicle
Papain SPT
Experimental group
Description:
Each forearm of the subject will be divided into two squared areas (4x4 cm). The provocations of three areas will be performed with 100 µg of papain by SPT lancets. To assess the potential importance of repeated pricks, papain will be applied by 1, 5 or 25 SPT pricks thought the skin. The last area will be exposed to cowage spicules (made chemically inert by autoclaving) soaked in 5 mg/ml papain solution.
Treatment:
Drug: Papain 25 SPT
Other: Cowhage
Drug: Papain 1 SPT
Drug: Papain 5 SPT

Trial contacts and locations

1

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Data sourced from clinicaltrials.gov

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