Not all toxin types, concentrations provide the same results

February 18, 2020

Understanding differences among preparations and dilutions of botulinum toxin type A can improve clinical practice, according to industry experts.

Different preparations and dilutions of botulinum toxin type A can produce different results for relaxing facial muscles, as well as improve skin elasticity, pliability and re-organize facial collagen. Understanding those differences could have implications for improved clinical practice, according to industry experts.

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The ability to use botulinum toxin type A to relax facial muscles and improve skin elasticity and pliability make it a highly sought-after treatment among patients. However, clinical evidence indicates not all types and concentrations provide the same results overall or in the same time frame.

In fact, a recent study published in the Journal of Cosmetic Dermatology revealed that using various botulinum toxin dilutions already actively employed in patient care can allow dermatologists to control and change the outcome for individual patients. But, for the best results, similar to a mild midfacial lift, providers should opt for less diluted toxins.

According to Rungsima Wanitphakdeedecha, M.D., lead study author, dermatologist and dermatologic surgeon based in Bangkok, Thailand, physicians should use this information in planning treatment and managing patient expectations.

“Although more diluted toxins may seem to produce better and faster fibroblast contraction,” she says, “in reality, more diluted toxins deliver lower total toxin dosages, thereby reducing toxin efficacy and longevity in clinical practice.”

The team posited that it was the fibroblast contraction itself that could be a potential mechanism for the positive lifting effect patients experience.

TYPES AND DILUTIONS
Prior to this study, it was unknown how intradermal botulinum toxin A injections prompted fibroblast contraction. It was also unclear which toxin or dilution ratio could be used to achieve the maximum satisfactory outcome for the individual patient. This is the first study to tackle this question, Dr. Wanitphakdeedecha says.

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To determine how different botulinum types and dilutions affect normal human dermal fibroblasts, her team tested various dilutions of botulinum toxins routinely used in practice, including onabotulinumtoxin (ONA), abobotulinumtoxin (ABO), praboutlinumtoxin A (PRABO), incobotulinumtoxin A (INCO) and letibotulinumtoxin A (LETI). Each toxin was tested in multiple dilutions, ranging from 1:2.5 to 1:10, and the team tested 50 fibroblasts per solution. Photographs and measurements taken every two hours from baseline 0 to 12 hours post-treatment revealed how much each fibroblast contracted over time. Based on study data analysis, she says, INCO, PRABO, LETI and ABO produced a decrease in fibroblast length at multiple dilutions. ONA was the only botulinum toxin A type that didn’t prompt a significant decrease in length at any time point or dilution ratio.

Among botulinum toxin A types, INCO was the only toxin that significantly shortened fibroblasts at all dilution levels examined. That result equates an almost-immediate lifting effect that is sustained for the length of time the toxic remains active, and the preferred INCO dilution ratio, she says, is 1:6.

While PRABO and LETI did cause fibroblast shortening at various dilution ratios from 1:7 and above, the impacts were interpreted to have short-term clinical effectiveness. ABO also instigated a significant fibroblast contraction at the 1:7 dilution, but the effect was seen only after 10 to 12 hours. ABO didn’t produce fibroblast shortening at any other dilution ratio or time period.

These results highlight the varying degrees of impact and efficacy patients experience with each type of botulinum toxin.

“We, therefore, conclude that different botulinum toxin A types induce fibroblast contraction to different extents and at different speeds,” she says.

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CLINICAL SIGNIFICANCE
Ultimately, Dr. Wanitphakdeedecha says, the study findings indicate botulinum toxin type A could be used effectively with no cytotoxic effect on fibroblasts. This finding supports what previous investigators have found in their evaluations and observations.

“Of clinical significance was our finding that, while the fibroblasts displayed a measurable decrease in length, their overall size did not change, and they did not disappear from the field of view,” she says. “Physicians should carefully consider the speed at which they hope to achieve an outcome, especially if fibroblast contraction may produce a visual tissue lifting.”

Consequently, for the best possible outcomes, dermatologists should use the data surrounding the efficacy of botulinum toxin type A dilutions and results to select the best product and dilution level for intradermal injections for face lifting.

Despite these results showing significant fibroblast contraction with many botulinum toxin types, Dr. Wanitphakdeedecha says further investigations are needed to determine the full extent and mechanism of this impact. Not only is a larger sampling of cells required, but a larger number of dilution levels should also be evaluated.

“An in-depth profile of these changes can provide botulinum toxin users with an understanding of the molecular mechanism behind the outcomes of different toxin-based aesthetic interventions and, also, to clarify why different commercial preparations product different results,” she says.