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Distinct neurotoxins that are neuromuscular paralyzing agents
Clostridium botulinum is a bacteria that causes botulism. It produces seven distinct neurotoxins that are neuromuscular paralyzing agents. The toxins are called botulinum toxin type A,B,C1,D,E,F, and G. Each neurotoxin consists of a 2 chain polypeptide linked by a disulfide bond as demonstrated in this picture. The larger polypeptide, called the heavy chain, is identical for all 7 toxin types. The smaller polypeptide, called the light chain, varies for each toxin subtype.
At the junction between the muscle and the nerve is an area called a neuromuscular junction. A similar junction occurs between the nerve and a sweat cell. The impulses from the nervous system travel down the nerve and cause a chemical messenger, acetylcholine, to be released from synaptic vesicles stored with the nerve endings.
Within the nerve ending itself are a series of proteins that are necessary to allow the synaptic vesicles to bind with the nerve endings to allow release of the acetylcholine. These proteins include SNAP-25, VAMP, and syntaxin. Botulinum toxin type A and E cut SNAP-25. Botulinum toxin B,D, F, and G cut VAMP. Botulinum toxin C1 cut syntaxin and SNAP-25. For botulinum toxin to work, it has to first bind to Zinc.
Botulinum Toxin A, commonly referred to as Botox®, Dysport®, or Xeomin®, is an artificially produced neuromuscular paralyzing agent that is now licensed by the FDA for blepharospasm, axillary hyperhidrosis, spasticity, cervical dystonia and wrinkles. Botulinum Toxin B, commonly referred to as Myobloc® or Neurobloc®, is an artificially produced neuromuscular paralyzing agent that is licensed by the FDA for cervical dystonia. When either botulinum toxin is injected into muscle the heavy chain binds to the nerve ending.
It is then internalized into the nerve terminal. In the nerve terminal botulinum toxin type A cuts the protein SNAP-25 and botulinum toxin type B cuts VAMP. The nerve terminal is no longer able to release acetylcholine.
When acetylcholine is no longer able to be released, the nerve impulses no longer make the sweat glands release sweat. Over time, the nerve creates new endings in a process called sprouting.
These new nerve terminals establish contact with the sweat glands and the effect of botulinum toxin wears off.
In the doses we commonly use, it is rare to get any systemic side effects. If one over injects an are near a muscle, then that muscle can be weakened and this is sometimes seen with palmar hyperhidrosis. This hand and finger weakness affects one abilities to do fine motor manipulation with the fingers but does not affect lifting strength. Of course, this is not permanent as the nerve regenerates the damaged protein and the neuromuscular junction begins working again. Botulinum toxin type B commonly causes dry mouth.
Botulinum toxins are being used off label for neuropathic pain. In this case, the toxin is felt to work by preventing the release of Substance P and CGRP from the pain terminals. The botulinum toxins can reach this area because there is no myelin around the pain nerve fibers.
Dr. Soparker and associates demonstrated that the use of Zytaze (a combination of Zinc and phytase) resulted in extending the benefit of botulinum toxin (at least Botox brand for blepharospasm and forehead wrinkles). Given the low cost, Dr. Loftus recommends all of his patients use Zytaze when using botox for hyperhidrosis.
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Harry S.(Patient Since 2012)
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David C.(Patient Since 2008)
Dr. Loftus takes the time to listen to his patients and create a plan of treatment. I continue to be very happy I learned about his practice.
Providing headache and hyperhidrosis care & wellness for over 25 years.
Dr. Brian Loftus, M.D.
Dr. Loftus is Board Certified in Headache Medicine as well as Neurology. In private practice since 1994, Dr. Loftus’ practice has gotten busier and he has decided to concentrate his practice in areas that he can make a particular difference compared to other neurologist. Therefore, Dr. Loftus has chosen to focus his neurology practice on headaches & head pain, headaches during pregnancy, and hyperhidrosis. In the spring of 2006, Dr. Loftus relocated his practice from the Texas Medical Center to Bellaire, just 5 miles west. He has been named a Texas Monthly “Super Doctor” and an H Texas magazine “Top Doctor” multiple times.