What are the differences in dosing between Dysport (abobotulinumtoxinA) and Botox (onabotulinumtoxinA) for various conditions?

Dysport vs. Botox Dosing Comparison

The most commonly used conversion ratio is 2.5-3:1 (Dysport:Botox), meaning approximately 2.5-3 units of Dysport are equivalent to 1 unit of Botox, though the optimal ratio varies by indication and anatomical site.

Conversion Ratios by Clinical Context

Aesthetic Applications (Glabellar Lines)

• For glabellar lines, a 2.5:1 ratio appears optimal, with 20 units of Botox demonstrating superior and more prolonged efficacy compared to 50 units of Dysport in head-to-head comparison 1
• This suggests that for cosmetic facial applications, the conversion factor may be closer to 2.5:1 rather than higher ratios 1

Hyperhidrosis Treatment

• For palmar hyperhidrosis, both 2.5:1 and 4:1 ratios show comparable efficacy 2, 3
• Using a 2.5:1 conversion (e.g., approximately 69 units Botox vs. 173 units Dysport), both preparations showed similar efficacy and safety profiles 2
• A 4:1 ratio (approximately 69 units Botox vs. 284 units Dysport) also demonstrated similar effectiveness, though Dysport showed a trend toward more rapid onset but higher incidence of local side effects (thumb-index pinch weakness) 3
• For axillary hyperhidrosis using 3:1 ratio (100 units Botox vs. 300 units Dysport), both achieved similar sweat reduction, but Botox demonstrated faster onset (1 week vs. 2 weeks) and longer duration (9 months vs. 6 months) 4

Cervical Dystonia

• For cervical dystonia, conversion ratios less than 3:1 are more appropriate 5
• Dysport at both 3:1 and 4:1 ratios showed superior efficacy compared to Botox for both impairment and pain reduction (p=0.02 and p=0.01 for Tsui scores, respectively) 5
• However, Dysport was associated with higher incidence of dysphagia (15.6% at 3:1 and 17.3% at 4:1 vs. 3% with Botox) 5
• This suggests that in cervical dystonia, the conversion factor should be less than 3:1 to achieve equivalent efficacy 5

Spasticity Management

• For focal spasticity, Botox dosing ranges from 100-300 IU based on predetermined diagrams, with efficacy comparable to oral baclofen except for ankle spasticity where Botox showed superiority 6
• The American College of Chest Physicians notes that botulinum toxin therapy for sialorrhea uses variable doses depending on whether botulinum A or B is used, and whether parotid or submandibular glands are targeted, though specific conversion ratios are not established 6

Key Clinical Considerations

Onset and Duration Differences

• Dysport tends to have faster onset (1-2 weeks) compared to Botox (1 week for hyperhidrosis applications) 2, 4
• Botox generally provides longer duration of effect in hyperhidrosis (9 months vs. 6 months for axillary treatment) 4
• These temporal differences may be clinically significant when selecting between preparations 4

Safety Profile Variations

• Higher Dysport doses (using larger conversion ratios) are associated with increased local adverse effects, particularly muscle weakness in adjacent areas 5, 3
• The incidence of dysphagia increases with Dysport in cervical dystonia applications 5
• Both preparations have well-established safety profiles across multiple medical specialties 7

Practical Dosing Algorithm

Step 1: Identify the indication

• Aesthetic (glabellar): Use 2.5:1 ratio 1
• Hyperhidrosis: Use 2.5-3:1 ratio 2, 4
• Cervical dystonia: Use <3:1 ratio (closer to 2.5:1) 5
• Spasticity: Follow FDA-approved Botox protocols (100-300 IU) 6

Step 2: Consider patient-specific factors

• If rapid onset is priority: Consider Dysport 2, 4
• If longer duration is priority: Consider Botox 4
• If minimizing local weakness is critical: Use lower conversion ratios or consider Botox 5, 3

Step 3: Monitor and adjust

• Assess efficacy at 2-4 weeks post-injection 2, 4
• Document duration of effect for future dosing adjustments 4
• Evaluate for local adverse effects, particularly muscle weakness 5, 3

Common Pitfalls to Avoid

• Do not assume universal 1:3 or 1:4 conversion ratios across all indications, as evidence suggests optimal ratios vary by anatomical site and indication 5, 3, 1
• Avoid using higher conversion ratios (>3:1) in cervical dystonia, as this increases adverse effects without proportional benefit 5
• Do not overlook the temporal differences between preparations when patient expectations or clinical needs favor rapid onset versus prolonged duration 4
• Be cautious with Dysport in areas where adjacent muscle weakness would be problematic, as higher doses increase this risk 3