This is a double-blind, vehicle-controlled study to evaluate the antipruritic efficacy of topical ketamine, amitriptyline, lidocaine, and a tri-combination of ketamine, amitriptyline and lidocaine (hereafter referred to as KeAmLi) using non-histaminergic itch provocations in healthy volunteers. Each participant will be pre-treated with the vehicle and 4 active topical creams, over two study visits (3 treatments on the 1st visit and 2 treatment on the 2nd visit). Each treatment will be applied to the randomized forearm test area for 30 minute, and then sensory testing will be performed. Sensory testing includes thermal and mechanical stimuli, and itch induction using the plant cowhage. These tests will reveal mechanistic information and potential cellular and molecular targets for improved antipruritic and analgesic therapies.
The purpose of this study is to examine the antipruritic efficacy of topical ketamine, amitriptyline, lidocaine, and a tri-combination of ketamine, amitriptyline and lidocaine (hereafter referred to as KeAmLi) using non-histaminergic itch provocations in healthy volunteers. The primary outcome is itch reduction (AUC) between the vehicle and active treatment (KeAmLi-combo). Secondary outcomes include modality-specific analgesic properties of the topically applied ketamine, amitriptyline, lidocaine, and KeAmLi-combo to controlled quantitative thermal and mechanical stimuli, which can improve our understanding of the mechanism of action of these substances in the context of topical therapy.