Pruritus Associated With OnabotulinumtoxinA Treatment of Neuromuscular Pain

February 2015 | Volume 14 | Issue 2 | Case Report | 199 | Copyright © 2015

Derek Ho BSa,b and Jared Jagdeo MD MSa,b,c

aDepartment of Dermatology, University of California Davis, Sacramento, CA
bDermatology Service, Sacramento VA Medical Center, Mather, CA
cDepartment of Dermatology, State University of New York Downstate Medical Center, Brooklyn, NY

Abstract

OnabotulinumtoxinA is one of the most widely used agents for cosmetic and medical treatment. Studies have shown that onabotulinumtoxinA is safe and effective with minimal adverse events, and is often well tolerated by patients. We present a patient who developed neuropathic pruritus five days after treatment with onabotulinumtoxinA for neuromuscular pain. This case highlights the treatment of pruritus associated with onabotulinumtoxinA and the therapeutic method to resolve the patient’s pruritus.

J Drugs Dermatol. 2015;14(2):199-200.

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CASE REPORT

A 65 years old Caucasian man with a past medical history of degenerative disc disease (DDD), chronic neck and low back pain, asthma, food and latex allergy, constipation, major depressive disorder (MDD), and post-traumatic stress disorder (PTSD) presented to dermatology clinic with a seven-month history of pruritus and “rash” on the neck. He stated that his pruritus started five days after he had onabotulinumtoxinA treatment in his neck and upper back for myofascial pain. He had pre-existing muscular pain from the neck down to inferior angle of scapula, and his physical medicine & rehabilitation (PM&R) physician performed onabotulinumtoxinA injections to the bilateral trapezius, rhomboid, cervical paraspinals, supraspinatus, and infraspinatus muscles to alleviate the neuromuscular pain in these areas. The injections included a total of 100 unit of onabotulinumtoxinA diluted in 5cc normal saline. His medications on presentation in dermatology clinic included morphine, methocarbamol, fluticasone, budesonide, ipratropium bromide, loratadine, cholecalciferol, quetiapine, fluoxetine, pantoprazole, polyethylene glycol, and docusate. Physical examination revealed linear, atrophic plaques, and hypopigmented, linear patches on the dorsal neck bilaterally with overlying excoriations. The diagnosis of pruritus associated with onabotulinumtoxinA treatment was made due to the temporal relationship. The patient was prescribed oral hydroxyzine, mupirocin (Bactroban) ointment, and camphor & menthol (Sarna®) lotion.

The patient returned to dermatology clinic three weeks later for follow-up and reported complete resolution of his pruritus since day 2 of treatment, and has stopped scratching the neck with significant healing of excoriations (Figure 1). His neck pain was still present at this visit.

DISCUSSION

We present this interesting case as we did not find other instances of pruritus associated with onabotulinumtoxinA treatment in the medical literature. OnabotulinumtoxinA is a neurotoxin that targets pre-synaptic axon terminals and inhibits acetylcholine secretion and results in muscle weakness. OnabotulinumtoxinA is FDA approved for medical treatment of strabismus and blepharospasm (1989), cervical dystonia (2000), and for cosmetic improvement of glabella lines (2002), and crow’s feet (2013). OnabotulinumtoxinA is one of the most widely used agents today for cosmetic treatments. According to the American Society for Dermatologic Surgery (ASDS), there were 1.8 million cases of wrinkle-relaxing injections (such as onabotulinumtoxinA) performed in 2013.1 This was a 20% increase from 2012.

Additionally, physicians have been using onabotulinumtoxinA for off-labeled treatments. Some of the off-labeled uses of onabotulinumtoxinA include treatment of neuromuscular pain, neurogenic overactive bladder, chronic migraines, hyperhidrosis and gustatory sweating syndrome, achalasia, and anal fissure.2 OnabotulinumtoxinA is generally considered a safe medication and is associated with rare serious adverse effects. In one study, serious adverse events were more likely to be associated with therapeutic uses than with cosmetic uses.7 Common adverse effects after cosmetic uses include lack of intended cosmetic effect, injection site reactions, ptosis, muscle weakness, and headache. Based upon a PubMed search and review of the literature combined with clinical experience, to our knowledge, there are no previously reported cases of pruritus after onabotulinumtoxinA treatment. The pruritus for our patient, compared with common side effects, was not transient in nature. There is a possibility that the patient’s presentation may have been an unmasking or precipitation of herpes zoster with

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