LAS VEGAS – Manufacturers of the approved botulinum toxins may claim that their product is superior, but there is likely little difference between them for cosmetic dermatology purposes, according to Dr. Michael H. Gold.
"The reality is, they all work about the same," said Dr. Gold at the annual meeting of the American Society of Cosmetic Dermatology and Aesthetic Surgery.
Dr. Michael H. Gold
Unfortunately, there are hundreds of other botulinum toxin products available on the Internet that have not been tested or approved. "This is where it gets scary," added Dr. Gold, a dermatologist in private practice in Nashville, Tenn.
There is little difference between the three botulinum toxins approved by the Food and Drug Administration – Botox (onabotulinumtoxinA, Allergan), Dysport (abobotulinumtoxinA, Medicis/Ipsen), and Xeomin (incobotulinumtoxinA, Merz) – and a fourth that is likely to be approved, he said. Phase III clinical data for PurTox (Mentor), are being reviewed by the FDA.
"It’s going to get approved eventually, and will have the same approval as all the others," Dr. Gold predicted. He said that his office was the first in the United States to have done research on all four neurotoxins. All are approved in Europe, where they sell under different names.
There are well-known dosing differences between Botox and Dysport. Dosing charts are easily available on the Internet. "If you use both of these, you should have these charts in your office," he said.
Some company-sponsored studies claim differences in efficacy between the neurotoxins, but the industry-sponsored trials should be read skeptically, he said.
A 20-patient study, sponsored by Medicis, showed that Dysport reached full effect faster than Botox when injected into the frontalis muscle, which was already known from the pivotal clinical trials, Dr. Gold said (J. Drugs Dermatol. 2011;10:1148-57).
A separate Medicis-sponsored study of 90 patients treated for lateral orbital rhytids reported that Dysport worked better than Botox (Arch. Facial Plast. Surg. 2011;13:380-6[doi:10.1001/archfacial.2011.37]). On average, the full effect was achieved in 1-2 days with Dysport, compared with 3 days for Botox. "But again, this is a sponsored study," not an independent evaluation, he noted.
Noninferiority studies comparing Xeomin (approved by the FDA in August 2011) and Botox showed that "they work exactly the same," Dr. Gold said. Xeomin’s approval is nearly identical to the approvals of the other botulinum toxins, and its duration is equivalent – "about 3 months," he said.
Xeomin does not contain hemagglutinin and, therefore, should have a lower risk for an antigen effect than Botox and Dysport. Whether or not this is significant is unclear, because there have been no antigen effects reported from the use of Botox or Dysport, he said.
PurTox also is a pure neurotoxin, "which means no resistance," but again it’s not clear if containing hemagglutinin is a risk, he said.
Another difference between the approved toxins is that the FDA required a two-point satisfaction grading scale in the Xeomin clinical studies, compared with a one-point satisfaction grading scale in the studies of Botox and Dysport. To show an effect from Xeomin, the satisfaction rating had to change from 3 to 1 or from 2 to 0.
In comparing the products, "the numbers and how you put them together are hard," Dr. Gold said. "Both Allergan and Medicis are going to tell us how great their product is, and the poor folks from Merz are going to have to tell us the difference between a one-point and two-point satisfaction" rating change.
Data for botulinum toxins that have not been FDA approved, however, are even harder to find.
Makers of neurotoxins available in other parts of the world have their own sponsored studies claiming equivalence to Botox. In China, for example, the search engine Alibaba turns up hundreds of botulinum toxin products for sale from at least 24 suppliers, said Dr. Gold. Most of them have no data to back them up, are sold illegally, and put the buyer at risk of a jail sentence.
An Allergan researcher analyzed a product from Nanfeng, China, and found that it contained 240 times the dose of botulinum toxin available in a vial of Botox. It killed every animal on which it was tested until it was diluted in a 1:240 ratio (J. Am. Acad. Dermatol. 2009;61:149-50).
Several well-manufactured neurotoxins are available in China that have gone through extensive Chinese regulatory processes, but caution is needed even with these, Dr. Gold said. In one open-label study comparing ChinaTox with Botox for the treatment of spasms and dystonia, five patients developed rash, even though the neurotoxin is less powerful than Botox.