Botox (onabotulinumtoxinA, Allergan), Dysport (abobotulinumtoxinA, Galderma) and Xeomin (incobotulinumtoxinA, Merz) do not have equivalent strain reduction, according to a study of glabellar line treatments. The results, researchers conclude, confirm non-interchangeability of these neurotoxins.
Researchers treated 73 treatment-naive females randomized to 20 units of Botox, 60 units of Dysport or 20 units of Xeomin in the glabella. They imaged patients 4, 14 and 90 days post injection and noted change in average dynamic glabella strain.
The researchers found that at day 4 the Botox group had a 42.1% strain reduction, vs. a 39.4% reduction in the Dysport group and 19.8% reduction in the Xeomin group. By day 14, there was a 66.1% strain reduction in the Botox patients; a 51.4% strain reduction in the Dysport group; and a 42.8% strain reduction among those receiving Xeomin. At day 90, the Botox group had a 43.5% strain reduction, vs. a 38.4% strain reduction among those receiving Dysport and a 25.3% strain reduction in the Xeomin group.
NEXT: A Practical Opinion
A Practical Opinion
"Evidence-based evaluation of cosmetic procedures is important but is difficult to quantify in many situations due to the myriad of variables including patients' individual muscle size, physiology, metabolism, drug resistance, depth of injection, etc.," Joe Niamtu, III, DMD, an oral and maxillofacial surgeon with a practice limited to cosmetic facial surgery in Richmond, Va., tells Cosmetic Surgery Times.
This study suggests that treatment dosage units of neuromodulator are not interchangeable. And all companies clearly state in their literature that units are not interchangeable, Dr. Niamtu says.
"Having said that, there is always an effort to estimate equipotent treatment doses amongst many drugs," Dr. Niamtu says. "We do this every day with anesthetic medications, analgesics, steroids and numerous substances. The average clinician is looking for an average consistency that can be approximated with a similar medication. This is not a bad thing, and helps doctors and patients make decisions that involve treatment and costs. We do the same thing with non-medical situations when we say that the effects of having a glass of wine are similar to drinking a single beer or a shot of whisky, or that taking one Alieve is the same as taking four Advil...."
From a purely scientific standpoint, these three neuromodulators may well not correlate in action to an algorithm of units, according to Dr. Niamtu.
"The fact that they do not correlate with dynamic strain is useful information, but clinically, in my experience, they correlate pretty closely. I feel that 20 Botox units, 25 Xeomin units and 60 Dysport units deliver a very similar clinical response and duration. I fully realize that this is anecdotal but it is also practical. Even with the utmost scientific study, different dosages of neuromodulators will have different effects on action and duration due to patient variability, and this is the hardest thing and may be impossible to quantify," he says.
The bottom line, according to Dr. Niamtu, who was not an author on the study, is that injectors should never dedicate an absolute number to interchangeability. This, he says, is a recognized tenant of experienced injectors.
"Fortunately, there is a wide safety margin in the cosmetic dosages of neuromodulators and erroring moderately in either direction poses little danger," Dr. Niamtu says.