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

Aalborg University

Status: Completed

Conditions: Itch

Treatments: Drug: Doxepin Topical; Drug: Papain; Other: Cowhage; Drug: Histamine

Study type: Interventional

Funder types: Other

Identifiers

NCT04554888

N-20200005 2nd project

Details and patient eligibility

About

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.

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: Crossover Assignment

Masking: Single Blind

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20 participants in 2 patient groups

Doxepin Application

Experimental group

Description:

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.

Treatment:

Drug: Doxepin Topical

Itch Induction

Experimental group

Description:

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.

Treatment:

Drug: Histamine

Drug: Papain

Other: Cowhage