There are many myths and misconceptions spread about botulinum toxin. Some of these are via the Internet, and some are by under educated injectors who take a weekend course. First of all, there is no such phenomenon as "fast metabolizers." Once the botulinum molecule attaches to the endplate, it is metabolized within 10 hours. At 24 hours, 60% of it is already excreted in the urine. Onset of action is 2 to 8 days. Everyone metabolizes the botulinum toxin at essentially the same rate.There are many factors associated with duration of action. The number of units per injection (and total dose), the dilution of the botulinum toxin, and operator experience are the 3 most common reasons for variations in results. I have nearly 20 years experience with botulinum toxin. I can tell you that the single greatest factor seems to be dilution concentration. While some surgeons reconstitute the Botox vial with anywhere from 2 to 8 mL, I dilute my vial with one mL of preservative-free saline. What this means is that the amount injected per injection site is more concentrated in a small area of the muscle, versus a large amount of fluid that leeches out of the muscle and into the soft tissues. Now, every injector is different in their dilution, their injection pattern, and the amount that they inject. People who routinely state that they are "fast metabolizers" and state that they are building up a "resistance" are, a majority of the time, "price shoppers." While some state that the non--protein bound botulinum toxins, i.e.,Xeomin, etc., are better because they do not lead to "resistance," this has yet to be scientifically proven. "Price shoppers" hop from office to office depending on who has the better price, who is offering a groupon, or who "charges by the area instead of per unit." If you are getting charged by the "area," you are either being overcharged or undertreated. I say this, because everybody has a different dosage and a different injection pattern, based on their anatomy. Charging by the area means that everybody is getting the same amount of botulinum toxin for the same area. Charging "per unit" means that you are getting exactly what you are paying for. "Price shoppers" never get the same treatment twice, because they are getting a different number of units, a different injection pattern, a different dilution, and a different experience with each new doctor that they go to. My advice is to stick with the doctor who gives you the best results, and pay per unit.... And do not keep switching injectors based on price. In the end, you will be wasting money. If you want to try a different botulinum toxin, try it for the sake of trying it. There is no scientific proof that protein-bound botulinum toxin leads to "resistance." Thank you very much for the question.Dr. David Mueller, DDS, FABOMS
