Now that more than one injectable formulation of botulinum toxin is on the market, the competition may help drive down prices.
Aside from potential price differences, little seems to distinguish the two injectable formulations of botulinum toxin type A on the market, Botox (Allergan) and Dysport (Medicis), Dr. Mark G. Rubin explained at the annual Hawaii Dermatology Seminar sponsored by Skin Disease Education Foundation.
"As of January 2010, I have injected over 700 patients with Dysport, all of whom have had Botox previously. In the vast majority of patients, they were unable to tell the difference," said Dr. Rubin, a dermatologist in private practice in Beverly Hills, Calif.
Price competition among various botulinum toxin type A brands will likely intensify when additional formulations, PurTox (Mentor) and Xeomin (Merz), receive expected Food and Drug Administration approvals.
These brands differ by parameters that include complexing proteins, dose equivalency, and need for refrigeration, but available data suggest few meaningful differences exist except for storage temperature. Both Botox and Dysport require refrigerated storage, while Xeomin and PurTox are stable when stored at temperatures up to 25º C, Dr. Rubin noted.
Perhaps the most hyped difference among botulinum toxin type A formulations is spread or diffusion following injection, a property also known as "field of effect." The evidence indicates little difference in the diffusion rates of Botox and Dysport, according to Dr. Rubin.
The active molecule in botulinum toxin type A is identical in all formulations. The difference is the complexing proteins that wrap around the active molecule. Data reported at the Toxins 2008 meeting in Baveno, Italy showed that, at physiological pH, the active molecule dissociates from complexing protein within 1 minute, after which diffusion should be the same for all formulations.
This interpretation received further support from data that showed the onset of action, efficacy, and duration of effect of Botox and Xeomin were nearly identical (Neurology 2005;64:1949-51; J. Neural Transm. 2006;113:303-12).
Additional results from other studies have also supported the notion that Botox, Dysport, and Xeomin all act in similar ways, he noted. Moreover, trials done for the FDA for treatment of blepharospasm and cervical dystonia showed similar adverse effect profiles for Botox and Xeomin, suggesting similar diffusion rates.
The only other area in which some of these products differ is in dosing. Xeomin and PurTox appear roughly similar in dosing to Botox, with 1 unit of each being about equivalent to 1 unit of Botox. Dysport, though, has different dosing: 2.5 units of Dysport generally have the same effect as 1 unit of Botox.
Dysport and Botox also have shown similar efficacy and adverse effect profiles in clinical studies, according to Dr. Rubin. In effects on frown lines, Botox has been found to have 84% efficacy, compared with 90% for Dysport. Median duration of response has been found to be 90 days for Botox and 117 days for Dysport. The incidence of headaches is reported to be 15% with Botox and 11% with Dysport, and the rate of blepharoptosis is 5% with Botox and less than 2% with Dysport, he reported.
Photo Courtesy Dr. Mark G. Rubin
Dr. Rubin disclosed being a consultant to Medicis, the company that markets Dysport, and to Revance Therapeutics, a company developing a topical formulation of botulinum toxin. SDEF and this news organization are owned by Elsevier.