Summary
Pruritus (itch) is an unpleasant
sensation inducing the desire to scratch. Chronic pruritus (> 6
weeks' duration) is a major and distressing symptom of many
diseases of dermatological, systemic, neurological or psychogenic
origin. Frequently, the underlying cause of pruritus cannot be
identified and causal therapy is not possible. Furthermore, chronic
pruritus is frequently refractory to conventional symptomatic
therapies. Recent research has revealed new neuronal mechanisms in
the skin and brain, suggesting novel therapeutic targets. The
efficacy of the corresponding innovative therapies has been proven
in recent studies and case series. For example, topical or systemic
application of specific agonists such as cannabinoids or
calcineurin inhibitors can influence neuroreceptors on sensory
nerve fibers of the skin and suppress pruritus. Itch-selective
neurons in the dorsal horn of the spinal cord can be targeted to
inhibit the transmission of pruritus to the somatosensory cortex.
Anticonvulsants, antidepressants and mu-opioid receptor antagonists
interfere with the sensation of pruritus in the central nervous
system. Chronic pruritus of any origin leads to considerable
psychosocial burden and impairs quality of life. Psychoeducational
interventions, stress training, training in social competence and
relaxation techniques are therefore important elements in the
treatment of chronic pruritus. Increasing knowledge of the
neurobiology of chronic pruritus offers new therapeutic strategies.
Currently, several clinical trials are investigating the efficacy
of new substances addressing neuroreceptors and cytokines in the
skin and central nervous system. The present review aims to provide
an overview of current neurophysiological and neurochemical
therapeutic models in chronic pruritus.