In some cases, injection technique may change as the patient ages. Women who previously received moderate doses of botulinum toxin in their late 20s to early 30s may benefit from lower doses as their facial anatomy changes. “Now that these patients are in their late 40s, they depend on their brow to actually lift up the lid. You do not want to knock out that mechanical action of the lateral frontalis,” says Dr. Cohen. “So there is a transition point for the forehead often in the mid- to late-40s where you may need to explain to these patients, ‘I know we’ve done it this way for a while, but we’re reaching a point where your forehead muscle is important for lifting up your brow and the brow lid positioning, so we’re not going to give you as high a dose as we did before. We want this to look natural, so we’re going to start using less and seeing you more frequently.’”
Determining the correct dosing is a matter of both experience and individual patient preference. Dr. Joseph notes that you do need to get feedback from your patients and customize treatment to their goals. “You need to ask, ‘What are your goals here? Can you describe to me what a homerun would be for you?’” he says. “Then you can tailor your dose to the patient. Sometimes that depends on how much money they want to spend. Once you obtain that information from a patient, you have to assess muscle mass. Have her actually use those muscles in front of your eyes and, with experience, you should be able to calculate in your head—that will take 10 units of Botox or that will take 15 units of Xeomin or 30 units of Dysport to get the result this patient wants.”
Dr. Wilson has his patients animate prior to treatment so he can mark his treatment areas, as well as during treatment to track the results and dosing. He recommends that injectors have new patients come back two weeks after treatment when the toxin is at peak effect. “You want to see exactly what the results are because everyone behaves differently and sometimes unpredictably,” he says. “You learn a lot about neuromodulation by bringing the patient back, and looking at how your dose and placement affected her. It’s not wise to bring them back too soon because it does take over a week for the toxin to have maximum efficacy. If you bring them back too soon and note asymmetry, you may re-treat before the toxin has taken full effect and make the asymmetry worse or overbalance.”
With three botulinum toxins currently available and more coming soon, one of the big questions is: Does it matter which toxin you use? “The reality of these products is that they are more similar than different,” says Dr. Cohen. That being said, he has found that certain patients seem to respond better to Dysport in the lantheral canthus. “It’s probably more of a dose phenomenon but sometimes endurance athletes, who are outdoors for long periods of time, have these really long crow’s feet that go from that orbital bone all the way to their scalp line,” he says. “For one reason or another, Dysport sometimes helps people with that longer, thicker, fan shape distribution of lines in the lateral canthus more than the other products.”
Dr. Wilson was the lead author of a study published in Plastic and Reconstructive Surgery (May 2016) that compared the dynamic strain of the three currently available toxins. “We looked at the movement of dots on the forehead to quantify exactly how much muscle—or movement—change there was given a typical dose of neurotoxin,” he says.
The researchers compared 20 units of Botox, 20 units of Xeomin and 60 units of Dysport. They found very similar results between Botox and Dysport, “to the point that the differences weren’t significant,” says Dr. Wilson. “But we did see significant differences in the efficacy—at least at the dose of 20 units—between Botox and Xeomin. What we also found was increased variability in individual patients when treated with Xeomin, unlike the other toxins.”
He posits that it could be the result of a slightly different formulation—Xeomin does have less proteins associated with it—but is more likely a dosing phenomenon. “One thing practitioners will do when they see a variable response—which we see with all of the neurotoxins—is increase the dosing, and often that will change the response,” says Dr. Wilson. “One thing we theoretically proposed in the paper is perhaps we should be using a higher dose of Xeomin to increase the true response.”
He notes that because Xeomin comes at a lower price point and doesn’t require refrigeration, providers can increase the dosing and still maintain a reasonable cost.
“I think what’s most important is that people try all of the toxins and see what works best in their hands,” says Dr. Wilson. “Bring all of the patients back and really look at their results. Make sure you’re taking photographs. This really helps you master neuromodulation. And remember that each patient is unique in her anatomy, in what she desires and in her response to a specific toxin, so you may have to vary your dose or change up your toxin depending on the patient.”
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Inga Hansen is the executive editor of MedEsthetics.