How is BoNT-A dosed for 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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BoNT-A dosing has to be individualized and is dependent upon muscles involved, prior response, and functional goals. Adverse effects are minimal; however, conditions requiring caution include patients who are hypersensitive to any ingredient in BoNT-A, those using aminoglycoside antibiotics, those with neuromuscular disease, and women who are pregnant or potentially lactating.

A consensus on the dosage has been recommended by the Spasticity Study Group. Examples of doses of BoNT-A in clinical trials for spasticity from MS, cerebral palsy, TBI, spinal cord injury (SCI), and stroke are as follows:

  • In MS, injection of 400 U of BoNT-A into the thigh adductors resulted in significant improvement in spasticity and hygiene compared with placebo [35]

  • In SCI, injection of 20-80 U of BoNT-A into the rhabdosphincter resulted in decreased urethral pressure and postvoid residual volume [36]

  • In adults suffering from cerebral palsy, injection of 1 U/kg of BoNT-A into the medial and lateral gastrocnemius of each leg resulted in an improvement in gait pattern compared with placebo [37]

  • For children with cerebral palsy, the American Academy of Neurology recommends offering injection of the calf muscles as a treatment option for equinus varus deformity (level A), but does not specify dosage [24]

  • In stroke, injections of 75-300 U of BoNT-A into the elbow and wrist flexors resulted in significant improvement in results of the Ashworth Scale compared with placebo [38]

Future trials of BoNT-A may be improved by attention to dose-effect response, dose escalation, broader randomization, and more uniform timing of injection in relation to the onset of neurologic deficit.

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