How does the efficacy of Dysport (abobotulinumtoxinA) compare to Botox (onabotulinumtoxinA) for common indications such as glabellar lines, cervical dystonia, and spasticity?

Dysport vs Botox Efficacy Comparison

For cervical dystonia and spasticity, Dysport (abobotulinumtoxinA) and Botox (onabotulinumtoxinA) demonstrate equivalent efficacy when properly dosed, while for glabellar lines the evidence is mixed with some studies favoring Botox at standard FDA-approved doses.

Cervical Dystonia

Both formulations are equally effective and should be offered as first-line treatment options for cervical dystonia. 1

• The American Academy of Neurology guidelines establish that abobotulinumtoxinA (Dysport) and rimabotulinumtoxinB have the strongest evidence and should be offered, while onabotulinumtoxinA (Botox) and incobotulinumtoxinA have similar efficacy and should be considered. 1

• All FDA-approved botulinum neurotoxin formulations are commonly used despite differing evidence levels. 1

• A head-to-head crossover study of 40 patients receiving both products demonstrated therapeutic equivalence, with treatment duration of 11.2 weeks for Botox versus 11.4 weeks for Xeomin (using a 1:1 conversion ratio), and the confidence intervals fell within the predefined equivalence range. 2

Dosing Considerations for Cervical Dystonia

• The conversion ratio between Dysport and Botox for cervical dystonia is 3:1 or potentially lower, meaning 300 units of Dysport equals approximately 100 units of Botox. 3

• Using a higher conversion ratio may lead to overdosing of Dysport. 3

• Effects typically last 3-6 months, and using the lowest effective dose at the longest interval maintains responsiveness over repeated cycles. 4

Spasticity (Upper and Lower Extremity)

For adult spasticity, both abobotulinumtoxinA and onabotulinumtoxinA are safe and effective for reducing muscle tone and improving passive function, and both should be offered as treatment options. 1

• The American Academy of Neurology establishes that abobotulinumtoxinA, incobotulinumtoxinA, and onabotulinumtoxinA are equally effective for upper extremity spasticity reduction and improvement of passive function. 1

• Botulinum neurotoxin reduces muscle tone and improves passive function (range of motion) but has less robust evidence for improving active function. 1, 5

• In one small trial (n=29) comparing botulinum toxin to oral baclofen for spasticity, no significant difference was found except for ankle spasticity, which favored botulinum toxin by 1 point on the Modified Ashworth Scale. 1

• The 2025 VA/DoD guidelines downgraded the recommendation from "strong for" to "weak for" based on evidence showing botulinum toxin may not have dramatically different efficacy from oral antispasmodics based on efficacy alone. 1

Practical Spasticity Management

• The conversion ratio for spasticity treatment is 3:1 (Dysport:Botox) or potentially lower. 3

• Comprehensive rehabilitation including physical therapy is essential since evidence for active function improvement remains limited. 5

• Dysport has a better cost-efficacy profile when properly dosed at the 3:1 conversion ratio. 3

Glabellar Lines (Cosmetic Use)

For glabellar lines, the evidence is conflicting, with Botox at the FDA-approved 20-unit dose showing superior efficacy in one study, while Dysport demonstrated earlier onset and longer duration in another study using different dose ratios.

Evidence Favoring Botox

• A double-blind pilot study found that Botox 20 units (the FDA-approved dose) provided better and more prolonged efficacy than Dysport 50 units for glabellar lines. 6

• Botox has extensive validation with over 80% of subjects satisfied through day 60, with median duration of response of 120 days for dynamic glabellar lines. 7

• Peak effect occurs between 30-60 days, and response progressively improves with subsequent treatments. 7

Evidence Favoring Dysport

• A triple-blind study of 85 patients showed Dysport had earlier onset of improvement compared to Botox in both glabellar and crow's feet regions. 8

• At 4 months, 83% of patients maintained improvement with Dysport versus 48% with Botox in the glabellar area when using a 2.5:1 dose ratio. 8

• Dysport provided longer duration of improvement in a higher percentage of individuals at dose ratios of 2.5:1 (glabellar) and 3:1 (crow's feet). 8

Reconciling the Conflicting Evidence

The key difference lies in dosing: the study favoring Botox used 20 units of Botox versus 50 units of Dysport (2.5:1 ratio), while the study favoring Dysport used higher equivalent doses. 6, 8 This suggests that when Dysport is dosed at 2.5:1 to 3:1 conversion ratios, it may provide comparable or superior duration, but at lower conversion ratios (like 2.5:1 in the negative study), Botox may perform better. 6, 8

Critical Dosing and Safety Considerations

• Units are not interchangeable between formulations due to differences in potency profiles. 9

• The appropriate conversion ratio is 3:1 (Dysport:Botox) for therapeutic indications, though cosmetic use may vary between 2.5:1 and 3:1. 3, 8

• Both products are contraindicated in pregnancy, neuromuscular disorders, and known allergy to botulinum toxin. 9

• Distant spread may occur but is uncommon, and several factors beyond the pharmaceutical preparation affect spread. 3

• If clinical resistance develops to one formulation, switching to an alternative product is reasonable after confirming adequate dosing and proper injection technique. 9