Does Neurotoxin Dose really matter for longevity?

What the Science Actually Shows

One of the most persistent misconceptions in aesthetic medicine is the idea that the dose of a neuromodulator doesn’t influence how long results last. Many patients believe that whether they receive fewer units or a standard dose, the duration of effect will be the same.

Current scientific evidence tells a different story.

Across all FDA-approved botulinum toxin type A products—including onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, prabotulinumtoxinA, and daxibotulinumtoxinA—dose has been repeatedly shown to impact both the strength and the duration of muscle relaxation. This effect is consistent across multiple brands, studies, and patient populations.¹–⁵

Why Dose Influences Duration

Botulinum toxins work by temporarily inhibiting acetylcholine release at the neuromuscular junction. The extent and persistence of this inhibition are dose dependent—higher doses produce more complete and longer-lasting chemodenervation within safe, studied parameters.¹–⁵

Manufacturers determine FDA-approved dosing through extensive clinical trials evaluating:

• Degree of wrinkle reduction
  
  

• Duration of effect
  
  

• Safety profile
  
  

• Adverse event rates
  
  

• Patient satisfaction
  
  

Because each formulation differs in molecular structure, diffusion characteristics, and potency, units are not interchangeable across brands, and dosing recommendations vary by product.¹¹,¹²

What the Research Shows

Multiple randomized, double-blind, dose-ranging trials have demonstrated a positive correlation between increased dose and prolonged clinical effect, particularly in dynamic upper-face lines such as the glabella.¹–⁵

Key findings across studies include:

• Higher doses resulted in greater wrinkle reduction
  
  

• Clinical improvement lasted significantly longer
  
  

• Safety profiles remained acceptable when dosing stayed within studied ranges
  
  

These findings have been replicated for onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and newer formulations such as daxibotulinumtoxinA.¹–⁵

Understanding FDA-Approved Dosing (Example)

To put this into context, the FDA-approved dosing for onabotulinumtoxinA in the upper face includes:

• Forehead lines: 20 units
  
  

• Glabellar lines (frown lines): 20 units
  
  

• Lateral canthal lines (crow’s feet): 24 units (12 units per side)
  
  

This totals 64 units for comprehensive treatment of the upper face according to labeling guidelines.⁶

In real-world practice, patients often receive significantly less than these studied doses. While conservative dosing can be appropriate in certain clinical scenarios, chronic under-dosing may lead to shorter-lived results, requiring more frequent retreatment and increasing overall cost over time.

Why Underdosing Happens

Injectors may intentionally lower doses due to:

• Budget constraints
  
  

• Fear of adverse effects
  
  

• Patient requests for minimal treatment
  
  

• Habitual use of historically low doses
  
  

Although under-dosing can produce a softer initial result, studies show that muscle activity often returns sooner, especially in strong or repeatedly treated muscles.¹–⁵

The Importance of Injector Expertise

Achieving long-lasting, natural-appearing outcomes is not simply about “more units”—it requires:

• Detailed facial anatomy knowledge
  
  

• Proper muscle targeting
  
  

• Individualized dosing strategies
  
  

• Risk mitigation for ptosis, asymmetry, or diffusion
  
  

This is why results can vary significantly between providers, even when using the same product. Chasing discounts or frequently switching injectors may seem cost-effective short-term, but often results in inconsistent outcomes and increased long-term expense.

Takeaway

The belief that dose does not influence neurotoxin longevity is not supported by current evidence. Well-designed clinical trials consistently demonstrate that appropriate, evidence-based dosing plays a meaningful role in both the effectiveness and duration of results.

When performed by an experienced injector using proper technique and individualized treatment planning, dosing within studied parameters can optimize both safety and patient satisfaction.

References

1. Joseph JH, Maas C, Palm MD, et al. Safety, pharmacodynamic response, and treatment satisfaction with onabotulinumtoxinA 40 U, 60 U, and 80 U in subjects with moderate to severe dynamic glabellar lines. Aesthetic Surgery Journal. 2022;42(11):NP1318–NP1327.
   
   

2. Polacco MA, Singleton AE, Barnes CH, Maas C, Maas CS. Dose-response relationship of incobotulinumtoxinA in glabellar rhytids. Aesthetic Surgery Journal. 2021;41(6):NP500–NP511.
   
   

3. Kerscher M, Fabi S, Fischer T, et al. IncobotulinumtoxinA demonstrates safety and prolonged duration in a dose-ranging study. Journal of Drugs in Dermatology. 2021;20(10):1052–1060.
   
   

4. Joseph JH, Eaton LL, Robinson J, Pontius A, Williams EF. Effect of increasing abobotulinumtoxinA dose on duration of efficacy. Journal of Drugs in Dermatology. 2016;15:1544–1549.
   
   

5. Carruthers J, Solish N, Humphrey S, et al. Injectable daxibotulinumtoxinA dose-ranging study for glabellar lines. Dermatologic Surgery. 2017;43:1321–1331.
   
   

6. BOTOX® Cosmetic Prescribing Information. July 2020.
   
   

7. Dysport® Prescribing Information. July 2020.
   
   

8. Xeomin® Prescribing Information. August 2021.
   
   

9. Jeuveau® Prescribing Information. January 2020.
   
   

10. Daxxify™ Prescribing Information. September 2022.
    
    

11. Brin MF, James C, Maltman J. Botulinum toxin type A products are not interchangeable. Biologics. 2014;8:227–241.
    
    

12. Samizadeh S, De Boulle K. Botulinum neurotoxin formulations: overcoming confusion. Clinical, Cosmetic and Investigational Dermatology. 2018;11:273–287.