What causes resistance to BoNT-A in the treatment of spasticity?

Updated: Jun 28, 2019
  • Author: Krupa Pandey, MD; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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Resistance to BoNT-A is characterized by absence of any beneficial effect and by lack of muscle atrophy following the injection. Antibodies against the toxin are presumed to be responsible for most cases of resistance. Resistance has been reported to occur in 3-10% of people.

Repeated, high-dose injections are far more likely to result in antibody formation than are less frequently repeated, low-dose injections. The smallest amount of BoNT-A necessary to achieve therapeutic benefit should be used, the interval between treatments should be extended for as long as possible, and booster injections should be avoided. When the amount injected totals the maximum of 400 U, further injections should not be given before 3 months after the last treatment.

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