Itch Relieving Effect of Botox: a Study in Healthy Subjects

Several studies have shown that botulinum toxin type A (BoNT/A) has an antipruritic effect due to the inhibition of acetylcholine and other pruritic factors, such as substance P and glutamate. For instance, subcutaneous BoNT/A improves itch accompanied to hand eczema, dermatitis, lichen simplex, and rhinitis. Furthermore, a double-blind, placebo-controlled study showed that BoNT/A reduced histamine itch intensity in healthy men. Since acetylcholine has been shown to mediate itch in atopic dermatitis, this study aims to test the itch relieving effect of BoNT/A on a non-histaminergic model for chronic itch. This non-histaminergic model using the plant cowhage induces itch by activating protease activated receptor 2 (PAR2) receptors, which play a role in the itch of atopic dermatitis, also making this model better suited to test the efficacy of BoNT/A to relive chronic itch.

Inclusion criteria

• Healthy volunteers between 18 and 50 years of age.
• Must be in general good health with no disease or physical conditions that would impair evaluation of itch and pain perception.
• No history of chronic itch or pain.
• Must abstain from the use of any systemic or topical anti-histamine, steroid, or pain relief medications from the week prior to the study till the completion of the study.
• Must abstain from the use of moisturizers on the arm.

Exclusion criteria

• Individuals under 18 or over 50 years of age.
• Inability to complete the required measures.
• The presence of an itchy skin disease.
• Diagnosis of diseased that would affect itch or pain perception (e.g. neuropathies).
• Currently enrolled in any investigational study in which the subject is receiving any type of drug, biological, or non-drug therapy.
• Use of oral, topical analgesics, or other medications known to interfere with itch or pain perception in the week prior to the study and throughout the study (e.g. antihistamines, anesthetics, opioids, neuroleptics, etc.).
• Use of emollients on the arms a week prior to the study and throughout the study.
• Use of anti-depressants, anti-psychotics, and illicit drugs.
• Known history of neuropathy, uremia, uncontrolled thyroid disease, and diabetes mellitus.
• Use of Botulinum toxin in the last year.
• Known allergies to Botox.
• Pregnant women. (Women of child bearing potential will undergo an human chorionic gonadotrophin (hCG) pregnancy test before Botox application).
• Hypersensitivity to any botulinum toxin preparation or to any of the components in the formulation.
• Infection at the injection site.
• Cardiovascular disease.
• Neuromuscular disorder (e.g., amyotrophic lateral sclerosis, myasthenia gravis, or Lambert-Eaton syndrome).
• Compromised respiratory function.
• Dysphagia.
• History of urinary tract infection.
• History of urinary retention.