Effect of Ketamine, Amitriptyline and Their Combination on Itch

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.