Effect of Ketamine, Amitriptyline and Their Combination on Itch

Aalborg University30 enrolled

Overview

Chronic itch affects approximately a fifth of the global population and is associated with substantial negative consequences for the affected individuals. Furthermore, there is a lack of efficient treat-ment options for chronic itch. Topical ketamine cream has been used successfully to relieve various forms of pain, and we hypothesize that topical ketamine relieves itch through a mechanism of action comparable to that in pain relief. The aim of this project is to evaluate the effects of ketamine both alone and in combination with amitriptyline on histaminergic and non-histaminergic itch induced by histamine and cowhage, respectively.

The main action of ketamine, 2-(2-chlorophenyl)-2-(methylamino)-cyclohexanone, is to antagonize the glutamate N-methyl-D-aspartate (NMDA) receptors. In the clinical setting, topical ketamine cream has been used successfully to relieve various pathogenic forms of pain. In addition to its pain-relieving effects, the cream was also reported to have itch-relieving properties in a very limited study. However, its efficacy on itch has not been established, and the mechanism of action remains uncertain. Ketamine cream is used not only by itself, but also in conjunction with other analgesics. One of these is amitriptyline, which may enhance the analgesic effects of ketamine. The aim of this human experimental study is to use the well-characterized anesthetic Ketamine, both alone and in combination with amitriptyline, as a tool to modulate different histaminergic and non-histaminergic itch modalities evoked by histamine and cowhage.

Study Type

INTERVENTIONAL

Allocation

Purpose

BASIC_SCIENCE

Masking

NONE

Enrollment

Conditions

Itch

Interventions

Ketamine 0.5%DRUG

Ketamine cream 0.5% will be applied in a 4x4 area in the forearm of each participant.

AmitriptylineDRUG

Amitriptyline cream 1% will be applied in a 4x4 area in the forearm of each participant.

ketamine + amitriptylineDRUG

A cream containing ketamine 0.5%, amitriptyline 1%, will be applied in a 4x4 area in the forearm of each participant.

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 drugs * Previous or current history of neurological, dermatological, immunological, musculoskeletal, cardiac disorder or mental illnesses (psychiatric diagnosis) that may affect the results (e.g., neuropathy, muscular pain in the upper extremities, anxiety, depression, schizophrenia etc.) * Moles, wounds, scars, or tattoos in the area to be treated or tested * Current use of medications that may affect the trial such as antihistamines and pain killers. * Participants had known allergy/discomfort to ketamine or amitriptyline * Skin diseases * Consumption of alcohol or painkillers 24 hours before the study days and between these * Acute or chronic pain and itch * Participation in other trials within 1 week of study entry (4 weeks in the case of pharmaceutical studies) * Lack of ability to cooperate

Locations (1)

Center for Neuroplasticity and Pain Faculty of Medicine, Aalborg University

Gistrup, Aalborg, Denmark

Outcomes

Primary Outcomes

Measuring itch by computerized Visual Analog Scale Scoring

We will ask the subjects to 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".