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Does Botox Cause Muscle Weakness over Time? With Exclusive Commentary From Steven Dayan, MD

NOTE: Only on SkinInc.com: Exclusive spa-focused commentary by Skin Inc. magazine advisory board member Steven Dayan, MD, follows this news item explaining why or why not this news should be concerning to your clients.

A new study by researchers at the Faculty of Kinesiology, University of Calgary, is raising questions about the therapeutic use of botulinum toxin A.

The study found that animals injected with clostridium botulinum type A neurotoxin complex experienced muscle weakness in muscles throughout the body, even though they were far removed from the injection site. The study also found that repeated injection induced muscle atrophy and loss of contractile tissue in the limb that was not injected with the toxin.

"We were surprised by the degree of muscle loss and atrophy in the limb that was not injected with the Botulinum toxin," says Rafael Fortuna, the lead author of the paper that will soon be published in the Journal of Biomechanics. "I think it's fair to say that the paper raises some important questions about the long-term therapeutic use of Botox, especially with children and adolescents."

The study used dosages that approximated therapeutic doses used to treat conditions like cerebral palsy where muscle contraction can't be controlled, resulting in muscle dystonia and spasticity. The study follows previous lab research from Walter Herzog, PhD, which found that botulinum toxin A, easily crosses the muscle membrane barrier, resulting in weakness in the surrounding (noninjected) muscles.

This study shows, for the first time, that in time Botulinum toxin A use also results in muscle weakness, atrophy and loss of contractile tissue in non-injected muscles far removed from the injection site."It may be that the benefits of using Botox for these kinds of therapeutic, medical uses, outweighs these potential long-term consequences," says Herzog, "however, I think this study raises some important issues that need to be followed to ensure the best possible outcomes for patients, in the long term."

Botulinum Toxin A is also used as a cosmetic treatment, where the drug paralyzes small muscles in the face to reduce the appearance of wrinkles. Herzog notes that while this study was looking at larger doses, the results should be valid for any application of the drug.

From www.sciencedaily.com, Dec 2, 2010

Exclusive Commentary from Skin Inc. magazine Advisory Board Member Steven Dayan, MD, Explaining Whether There is Cause for Concern

“The recent article published in the Journal of Biomechanics evaluates the effects of high doses of Botox on the muscles being treated and the surrounding muscles in New Zealand rabbits. The authors conclude that Botox can lead to muscle wasting, fatty infiltration into the muscles and long-distance weakness of other untreated muscles that may result in cumulative defects to the distant muscle groups. This study, although being debated by the media, has little to no significance to the cosmetic clinical treatment that is used today. First of all, they gave the Botox to rabbits. Rabbits are very different than humans. Secondly, they gave very high doses of Botox and gave it monthly for six months. This would be the equivalent of giving 240 units of Botox to someone every month for six months! That is very unrealistic. The normal dose of Botox given cosmetically is around 30 units. The 240 units used in the study are seven times the normal cosmetic dose.

"Their conclusion that surrounding muscles were effected with long-term weakness is also a poorly supported statement. They tested nearby muscle groups. When giving high doses of Botox, who is to say that some of the Botox didn’t diffuse over to the nearby muscles by overwhelming natural transport mechanisms? Why didn’t they look at muscle groups in the forelimbs or shoulders if they wanted to test distal spread? Perhaps the opposite hind limb in rabbits is naturally underutilized when one hind limb is effected? They didn’t do biochemistry studies to confirm if Botox was taken up in those nearby muscle groups. Additionally, if Botox long-term leads to muscle atrophy and fatty infiltration, that would be welcomed by many of my patients, because that could mean that Botox may have long-lasting effects. But in all likelihood, the muscle activity would return once the Botox was stopped. The authors didn’t test this though. Botox has been used clinically for 25 years in both high and low doses with an unparalleled safety record and, when used as indicated for cosmetic use, the safety record is outstanding. Bottom line: Botox is still one of the safest and most reliable cosmetic treatments available.”

Steven Dayan, MD

Clinical Assistant Professor, University of Illinois

Adjunct Professor, DePaul University

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