Editor’s Note
**Editor’s Note:** This article explores the rare but real phenomenon of neurotoxin resistance, where patients develop neutralizing antibodies that reduce the effectiveness of botulinum toxin treatments. We clarify the distinction between true biological resistance and other factors that may diminish treatment response.
Neurotoxin resistance is a phenomenon that explains a patient’s “diminished or absent response to botulinum toxin treatments despite receiving the appropriate dose, proper injection technique and treatment in the correct muscles,” explains New York dermatologist Dr. Shereen Teymour. True neurotoxin resistance occurs when the body develops neutralizing antibodies that reduce the effectiveness of botulinum toxin. Fortunately, true biological resistance is quite uncommon, only occurring in about 0.5 percent of patients, according to a study.
“Repeated exposure to any biologic protein has the potential to stimulate an immune response,” says Southlake, TX dermatologist Janine Hopkins, MD. However, clinically significant resistance is very rare in aesthetic practice, particularly because cosmetic doses are relatively low with treatment spaced several months apart. True neurotoxin resistance is thought to occur when the immune system develops neutralizing antibodies that bind to the active botulinum toxin and prevent it from working effectively.
That said, there are still several factors that may increase your theoretical risk of antibody formation, including frequent treatment, very high cumulative doses or receiving “touch-up” injections too soon after your initial treatment. “There has also been discussion that accessory proteins, sometimes called complexing proteins, present in some formulations could contribute to immunogenicity, although the overall clinical significance remains an area of ongoing research. Regardless, clinically meaningful resistance remains uncommon in cosmetic dermatology,” says Dr. Teymour.
Dr. Teymour says that Xeomin is often considered a reasonable option when there is a concern for immunologic resistance because “it contains only the purified 150-kDa botulinum toxin molecule and does not contain the accessory (complexing) proteins found in some other botulinum toxin formulations. For this reason, Xeomin is sometimes referred to as a ‘naked’ neurotoxin.”
Theoretically speaking, reducing unnecessary protein exposure with a neurotoxin like Xeomin may potentially lower the risk of stimulating an immune response for those who are clinically resistant. “Though reducing unnecessary bacterial proteins may reduce the overall antigenic exposure, definitive evidence that this translates into lower rates of clinically significant resistance in aesthetic patients is still evolving,” says Dr. Teymour. She further explains that if a patient has in fact developed antibodies against the accessory proteins rather than the neurotoxin itself, some clinicians have reported improved responses after switching to Xeomin.
