The risk of immunoresistance and secondary nonresponse to botulinum toxin (BTX) is being overlooked in aesthetic practice and may lead to medicolegal action against practitioners if patients are not forewarned, a new consensus statement advises.

While the potential for BTX to stimulate neutralising antibodies (NAbs) that counteract its biological activity is recognised in medical usage, there is low awareness around it rapidly growing use in aesthetic procedures, according to a paper published by the journal of the American College of Plastic Surgeons

After reviewing the evidence on BTX immunoresistance, an international panel of specialists in dermatology and cosmetic medicine – including Australian co-authors –  concluded that rates related to aesthetic procedures were likely to be underestimated as BTX usage expands by millions of procedures per year.

Evidence from use of BTX in medical procedures showed that reported NAb formation frequency in conditions such as dystonia ranged from 1.3% to as high as 27.6%, they noted.

Rates of secondary nonresponse would vary according to the formulation used, dosage, purity and other variables such as duration and frequency of injection.

Estimates of immunoresistance in aesthetic applications were difficult to make because published evidence was inconsistent and often consisted  of case reports, the authors said.

However since doses of BTX in aesthetic practice were increasing in off label uses, and there would be cumulative effects of over a lifetime, it would be reasonable to expect similar trends in immunoresistance as seen in medical practice.

In a hypothetical example, an aesthetic patient might start BTX treatment at the age of 30 influenced by lifestyle and financial considerations ,and have frequent repeat BTX treatments at different locations and practitioners. With an increasing duration of treatment they might require increasing doses of BTX to sustain the effects and be at risk of NAb formation and secondary nonresponse, the authors suggested

“This potentially leads to suboptimal outcomes if this patient later develops a chronic medical condition that requires [BTX] treatment. Such cases may have medicolegal implications, especially if risks such as NAb-related secondary nonresponse were not thoroughly discussed with the patient before treatment,” they wrote.

In addition to patient assessment and counselling, “practitioners need to recognise immunogenicity as a potential complication that might affect future therapeutic use and strive to minimise modifiable risk factors,” the authors suggested.

Best practices to minimise secondary nonresponse include using the smallest dose of BTX needed to achieve the desired outcome, having longer intervals between treatments and avoiding ‘top ups’  and boosters, they said.

“With millions of aesthetic [BTX]  treatments performed worldwide, especially off-label applications involving higher doses than traditional on-label indications, more practitioners may expect to encounter possible cases of NAb-related secondary nonresponse,” they said

“Aesthetic practitioners are obliged to make treatment decisions in accordance with the key pillars of medical ethics and should strive to minimise modifiable risk factors,” they concluded.