Botulinum Toxin 2013: Where are we now?
Joel Cohen, MD
It is important that clinicians understand the molecular structure of Botulinum neurotoxin type A. Botox and Dysport have an envelope of protein around it; xeomin; however, does not have these accessory proteins.
Differentiating Botulinum Toxins
Regulatory agencies worldwide have recognized that these products are not interchangeable. The units of biologic activity in each available product cannot be compared or converted into the units of any of the other available products, nor can the doses or preparations be interchanged. You need to learn how to use each product effectively.
New Data on Xeomin
In a head to head study comparing Xeomin to Botox for the treatment of cervical dystonia both products appear to be effective for this subset of patients.
What about the aesthetic use of Xeomin?
It’s important to note that the changes in FDA requirements over the fast few years are quite profound. The FDA now requires a two-grade improvement, whereas when Botox was conducting it’s clinical trials, the FDA only required a one-grade improvement. Overall, Xeomin and Botox appear to have similar efficacy.
A small Xeomin study for the treatment of crow’s feet (N = 21) also demonstrated similar efficacy between both products.
Science and Data to Consider
We have very good safety and efficacy studies available. Patients seem to have a better quality of life, and look and seem happier. It is important to understand where not to inject. Over the last few years, we have seen success in treating crow’s feet and may begin to see more of a focus in this area. It’s imperative to look at each patient’s musculature when injecting toxins so as to achieve maximum results.
What’s new with botulinum toxin-A?
Dermatologists should be cautious of the dangers associated with delivering fillers and toxins simultaneously.
A recent publication by Dr Koshy (April 2012) advocated the use of a proprietary zinc formulation to augment botulinum toxin efficacy for patients using toxins for aesthetic purposes. This paper presented many problems, mainly the fact that zinc augmentation of the botulinum toxin efficacy effect has never been described. And the actual study was done very poorly. Where does the idea to use zinc come from?
The neuronal receptor for botulinum toxin is comprised of a heavy chain and light chain. A zinc dependent metalloprotease is responsible for cleaving the botulinum protein for it to be effective. The article (above) suggests that we are zinc deficient and; therefore, we don’t have enough zinc. This effect remains to be seen and we should be skeptical of this study.
If we look specifically at dosing, data used to suggest that higher botulinum toxin type A doses resulted in greater efficacy and longer duration of the effect. In 2008, experts developed a consensus (rewrite from 2004) with regards to how to best achieve an optimal, relaxed and natural outcome using botulinum toxin type A. This resulted in basically cutting the forehead doses in half.
We have choices and dermatologists should review the various recommendations and guidelines in order to obtain the best effect for their patients.
Patient satisfaction is a key aspect of facial aesthetics. Various studies have looked at patient reported outcomes among the products available; however, it is often difficult to compare the results.
With regards to the use of Dysport, when patients were asked, it seemed to work within a couple of days. No one recorded that information with Botox. In general, botulinum toxin type A begins to work in about two days.
Across the board, looking at the glabellar lines, the duration of botulinum toxin type A is about four months in about 50% of patients. Data has also demonstrated that patients tend to have a cumulative effect; in that, the efficacy with repeated injections is extended over a longer period of time.