Confusion about diffusion and the art of misinterpreting data when comparing different botulinum toxins used in aesthetic applications

AbobotulinumtoxinA for Facial Rejuvenation: What Affects the Duration of Efficacy?

AbobotulinumtoxinA (Dysport) has a long history as a safe and effective treatment option for aesthetic rejuvenation. One of the key measures of botulinum toxin efficacy is the persistence of clinically meaningful results. The duration of efficacy depends on different factors, many of which can be controlled by the clinician to better achieve their desired results. In this review, we discuss how dose, individual patient variation, and injection technique affect the duration of botulinum toxins. Increased duration may result from increased dose or more precise placement of the toxin in the muscle. The varying anatomy and behavior of patients can affect duration as well. Measures of duration in clinical studies vary, but both a 1-grade improvement on the glabellar line severity scale and patient-reported outcomes are key measures. The clinical effects of Dysport can last up to 5 months, and patients in Dysport clinical studies remained satisfied with treatment for up to 6 months. Dysport has a legacy of safety, efficacy, and high subject satisfaction demonstrated through studies and clinical experience. Building on that legacy by correctly dosing the subject, properly accounting for the individual subject anatomy and behavior, and using specific injection techniques can help ensure that your patients have the longest lasting results.

Do complexing proteins provide mechanical protection for botulinum neurotoxins?

Botulinum toxin (BT) consists of botulinum neurotoxin and complexing proteins (CPs). CPs might provide mechanical protection for botulinum neurotoxin. As incobotulinumtoxinA (INCO, Xeomin®) does not contain CPs, we wanted to compare its mechanical stability to that of onabotulinumtoxinA (ONA, Botox®) containing CPs. For this, ONA and INCO were reconstituted without mechanical stress (NS) and with mechanical stress (WS) generated by a recently introduced stress test. Potencies were then measured by the paralysis times (PTs) in the mouse diaphragm assay. ONA-PT was 75.8 ± 10.3 min (n = 6) under NS and 116.7 ± 29.8 min (n = 6) under WS (two-tailed t test, p = 0.002). Mechanical stress increased the ONA-PT by 35.0% on the Growth Percentage Index. INCO-PT was 66.0 ± 7.0 min for NS and 76.0 ± 1.0 min for WS (t test, p = 0.129). Mechanical stress increased the INCO-PT by 13.2% on the Growth Percentage Index. Our data show that mechanical stress inactivates a CP-containing BT drug, but not a CP-free BT drug. We conclude that CPs do not provide protection against mechanical stress, supporting the view that CPs are not necessary for therapeutic purposes.

The Dilution Confusion: Easy Dosing for Botulinum Toxins

Aesthetic practitioners prefer various reconstitution volumes for botulinum toxins (BoNTAs). Some injectors prefer larger volumes of bacteriostatic normal saline (NaCl) to achieve a larger diffusion in certain areas and a smaller volume for more precise administration of the BoNTA. Some practitioners believe dilution volumes do not matter at all in relation to spread or diffusion, asserting the diffusion area is simply dose-related. It can get confusing when there is more than one injector in an office, different volumes of saline, and more than one type of syringe to administer the neurotoxin. This leaves possibilities for confusion and dosage errors. This article explores four steps to take the confusion out of reconstituting BoNTAs and delivering accurate and consistent doses within a medical office.

Botulinum toxin type A products are not interchangeable: a review of the evidence

Botulinum toxin type A (BoNTA) products are injectable biologic medications derived from Clostridium botulinum bacteria. Several different BoNTA products are marketed in various countries, and they are not interchangeable. Differences between products include manufacturing processes, formulations, and the assay methods used to determine units of biological activity. These differences result in a specific set of interactions between each BoNTA product and the tissue injected. Consequently, the products show differences in their in vivo profiles, including preclinical dose response curves and clinical dosing, efficacy, duration, and safety/adverse events. Most, but not all, published studies document these differences, suggesting that individual BoNTA products act differently depending on experimental and clinical conditions, and these differences may not always be predictable. Differentiation through regulatory approvals provides a measure of confidence in safety and efficacy at the specified doses for each approved indication. Moreover, the products differ in the amount of study to which they have been subjected, as evidenced by the number of publications in the peer-reviewed literature and the quantity and quality of clinical studies. Given that BoNTAs are potent biological products that meet important clinical needs, it is critical to recognize that their dosing and product performance are not interchangeable and each product should be used according to manufacturer guidelines.

Efficacy and safety of incobotulinum toxin A in periocular rhytides and masseteric hypertrophy: side-by-side comparison with onabotulinum toxin A

BACKGROUND

Incobotulinum is a newly developed botulinum toxin A in which the complexing proteins had been removed.

OBJECTIVE

The aim was to compare the efficacy and safety of incobotulinum with onabotulinum in treating periocular rhytides and masseteric hypertrophy.

METHODS

A randomized, double-blind, split-face study was planned. Fifty-six patients were treated for periocular rhytides and the other 56 patients were treated for masseteric hypertrophy. Onabotulinum was injected on one side of the face and incobotulinum was injected on the other side of the face. The degree of periocular rhytides and masseteric hypertrophy was rated using Fitzpatrick Wrinkle Classification System (FWCS) and 10-point visual analogue scale (VAS) (0: the minimum to 10: the maximum). Objective and subjective rating was performed at pretreatment and every posttreatment follow-up visit by investigators and subjects.

RESULT

The efficacy and safety of incobotulinum were not inferior to those of onabotulinum in treating periocular rhytides and masseteric hypertrophy up to 16 weeks after injection. There were no noteworthy differences in the onset time of effect between two botulinum toxins for periocular wrinkles and masseteric hypertrophy. No adverse event was reported.

CONCLUSION

Incobotulinum provided non-inferior efficacy and safety for the treatment of periocular rhytides and masseteric hypertrophy compared with classic onabotulinum.

IncobotulinumtoxinA (Xeomin): background, mechanism of action, and manufacturing

IncobotulinumtoxinA is the third botulinum neurotoxin type A (BoNTA) to be approved for aesthetic use in the United States. This article introduces the new product with an overview of clinical applications and a discussion of the neurotoxin's molecular structure. The role and clinical relevance of complexing proteins in BoNTA products are discussed. Finally, incobotulinumtoxinA's mechanism of action is described.

Current aesthetic use of abobotulinumtoxinA in clinical practice: an evidence-based consensus review

The amount and complexity of scientific and clinical evidence for aesthetic use of botulinum neurotoxin type A (BoNT-A) has expanded rapidly in recent years, especially for abobotulinumtoxinA, necessitating reassessment of current knowledge about aesthetic use of abobotulinumtoxinA and other BoNT-A preparations. A committee of 13 plastic surgeons, facial plastic surgeons, and dermatologists engaged in a live discussion of information from a systematic literature review and an Internet-based survey of their beliefs and practices. The committee achieved consensus on most issues. It was concluded that doses of different BoNT-A preparations cannot be interconverted with a fixed ratio. The size of the "field of effect" is difficult to measure, and comparisons between preparations have yielded equivocal results. Nonresponse due to neutralizing antibodies appears exceedingly rare with currently available BoNT-A preparations and of little concern clinically. BoNT-A dose, injection depth, and injection technique should be adjusted according to the anatomic area being treated and each patient's individual characteristics and goals. Aesthetic use of BoNT-A has a good safety profile. Most adverse events are minor and related to the trauma of injection, although special care is needed in certain anatomic areas. Detailed recommendations for treatment of different anatomic areas are presented. BoNT-A products are often used in conjunction with other treatment modalities (eg, fillers and resurfacing), but little agreement was reached on best practices. The findings reported in this consensus document may serve as a practical guide for aesthetic practitioners as they apply the latest knowledge about BoNT-A in providing their patients with optimal care.

Diffusion of botulinum toxins

BACKGROUND

It is generally agreed that diffusion of botulinum toxin occurs, but the extent of the spread and its clinical importance are disputed. Many factors have been suggested to play a role but which have the most clinical relevance is a subject of much discussion.

METHODS

This review discusses the variables affecting diffusion, including protein composition and molecular size as well as injection factors (e.g., volume, dose, injection method). It also discusses data on diffusion from comparative studies in animal models and human clinical trials that illustrate differences between the available botulinum toxin products (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB).

RESULTS

Neither molecular weight nor the presence of complexing proteins appears to affect diffusion; however, injection volume, concentration, and dose all play roles and are modifiable. Both animal and human studies show that botulinum toxin products are not interchangeable, and that some products are associated with greater diffusion and higher rates of diffusion-related adverse events than others.

DISCUSSION

Each of the botulinum toxins is a unique pharmacologic entity. A working knowledge of the different serotypes is essential to avoid unwanted diffusion-related adverse events. In addition, clinicians should be aware that the factors influencing diffusion may range from properties intrinsic to the drug to accurate muscle selection as well as dilution, volume, and dose injected.

Field effect of two commercial preparations of botulinum toxin type A: a prospective, double-blind, randomized clinical trial

BACKGROUND

The dose equivalence of commonly used commercial preparations of botulinum toxin type A, Dysport (abotulinumtoxinA [ABO] 500 U, Ipsen Biopharm Limited, Wrexham, United Kingdom) and Botox (onabotulinumtoxinA [ONA] 100 U, Allergan, Irvine, CA), remains unclear.

OBJECTIVE

We sought to evaluate the field effect for ABO and ONA at dose equivalences of 2.5:1.0 U and 2.0:1.0 U, in both muscular and sweat gland activity.

METHODS

In all, 59 female patients with forehead wrinkles were enrolled. Patients were randomized for dose equivalence between ABO and ONA, group A (2.0:1.0 U, ABO:ONA) or group B (2.5:1.0 U, ABO:ONA) administered in the frontalis muscles. Clinical assessment, Minor test, and electromyography evaluations were performed at baseline, 28 days, and 112 days.

RESULTS

In group B, the field of anhidrotic effect of ABO showed a greater area and larger horizontal diameter than ONA at 28 and 112 days. At maximum frontalis muscle activity (day 112) patients receiving ABO demonstrated greater improvement based on the Wrinkle Severity Scale. No differences were found in frontalis muscle activity at rest between groups A and B based on results of Wrinkle Severity Scale, electromyography, and interindividual variability data at 28 and 112 days.

LIMITATIONS

Currently, there are no objective measurements other than electromyography to evaluate the field effect of botulinum toxin type A in muscles.

CONCLUSION

At a dose equivalence of 2.0:1.0 U (ABO:ONA), similar field effects were found for both muscle and sweat gland activity. At a higher dose equivalence of 2.5:1.0 U (ABO:ONA), injections of ABO showed greater area and larger horizontal diameter in field of anhidrotic effect at 28 and 112 days than ONA.

Profile of Xeomin® (incobotulinumtoxinA) for the treatment of blepharospasm

Even though conventional botulinum neurotoxin (BoNT) products have shown successful treatment results in patients with benign blepharospasm (BEB), the main, potential long-term side effect of BoNT use is the development of immunologic resistance due to the production of neutralizing antibody to the neurotoxin after repeated injections. Xeomin^® (incobotulinumtoxinA), a unique botulinum neurotoxin type A (BoNT/A) drug free of complexing proteins otherwise contained in all conventional BoNT/A drugs, was recently approved by US Food and Drug Administration for the treatment of cervical dystonia or blepharospasm in adults. The newly approved BoNT/A drug may overcome this limitation of previous conventional products, since it contains pure neurotoxin (150 kDa) through a manufacturing process that separates it from complexing proteins such as hemagglutinins produced by fermentation of Clostridium botulinum. Many studies have also shown that Xeomin^® has the same efficacy and safety profile as complexing protein-containing products such as Botox^® and is exchangeable with Botox^® using a simple 1:1 conversion ratio. Xeomin^® represents a new treatment option for the repeated treatment of patients with blepharospasm in that it may reduce antibody-induced therapy failure. But, long-term comparative trials in naïve patients between Xeomin^® and conventional BoNT/A drugs are required to confirm the low immunogenicity of Xeomin^®.

Complexing proteins in botulinum toxin type A drugs: a help or a hindrance?

Botulinum toxin type A is a high molecular weight protein complex containing active neurotoxin and complexing proteins, the latter of which, it is believed, protect the neurotoxin when in the gastrointestinal tract, and may facilitate its absorption. Comparisons of conventional botulinum toxin type A drugs that include complexing proteins with the complexing protein-free formulation of Xeomin^® strongly suggest that complexing proteins do not affect diffusion of the active neurotoxin. Studies of Xeomin have also shown that complexing proteins do not enhance product stability in storage. However, complexing proteins may stimulate antibody development against botulinum toxin type A. Numerous observational studies have been published showing that some patients receiving conventional botulinum toxin may develop neutralizing antibodies, leading to antibody-induced therapy failure. Studies have shown that Xeomin is not associated with the development of neutralizing antibodies in animal models or in patients. In conclusion, complexing proteins do not contribute to the stability of botulinum toxin type A drugs and do not contribute to their therapeutic effects, but may be associated with a secondary nonresponse due to the development of neutralizing antibodies.

Facial rejuvenation for middle-aged women: a combined approach with minimally invasive procedures

Facial rejuvenation is a significant process involved in restoring youthfulness. The introduction of less invasive procedures has increased acceptance of such procedures. Often a combination of different techniques allows individualized treatment with optimal outcomes. Furthermore, this leads to a natural look without a significant downtime. We report herein the use of such a combined approach in middle-aged women with particular emphasis on botulinum toxin type A, dermal fillers, and chemical peels.

[Different botulinum toxins and their specifications]

Botulinum neurotoxin A was the first developed for therapeutic and then esthetic uses, Botox first and then Dysport. These two products differ on a few points, explaining their nonequivalence of units: American and British tests of the mouse LD50 units based on solutions that were not identical and 500microg vs 150microg serum albumin dose in the excipient. The neurotoxin- accessory protein complexes were also different: 900 kDa homogeneous for Botox, 500 kDa heterogeneous for Dysport, giving greater diffusion for Dysport, but this is under debate and could result from an excessive conversion ratio. Clinical comparative studies, often with weak methodology, have defined an ideal ratio between these two products, guaranteeing efficacy, but without an overly pronounced diffusion. In the first publications for neurological and ophthalmological indications, the conversion ratio between Dysport and Botox was high, 4:1, and sometimes higher. However, today, particularly for cosmetic indications, the trend is toward a much lower ratio, 2.5:1, or perhaps less for dyshidrosis. This lower ratio has an economic incidence: Dysport is less expensive and therefore more competitive. The price of Dysport's cosmetic product, Azzalure, compared to the price of Vistabel, which is Botox's cosmetic presentation, has not yet been defined in France. The other A toxins, Xeomin, and the Asian toxins, MyoBloc (botulinum toxin type B), tested compared to Botox, have a slightly lower efficacy.