Botulinum Toxin in Aesthetic Medicine: Myths and Realities.

BACKGROUND: Several formulations of Botulinum toxin serotype A (BoNT-A) for aesthetic indications are available, with numbers likely to increase. Preparations are not interchangeable, based on dose unit comparisons. OBJECTIVE: Numerous myths and misconceptions regarding the use of BoNT-A for aesthetic indications have arisen, which this review aims to lay to rest. MATERIALS AND METHODS: This review assesses evidence for and against each of the most common myths regarding BoNT use in aesthetics. RESULTS: BoNT-A neurotoxin/protein complexes are irrelevant to the toxin's therapeutic/aesthetic indications. BoNT-A neurotoxin/protein complexes do not influence movement from injection site or immunogenicity. Any relationship between neutralizing antibody formation and clinical response is complex and clinicians should consider other factors that may induce an apparent loss of clinical response. Diffusion appears predominately, perhaps exclusively, dose dependent. Careful placement and correct dosing optimizes likelihood of good outcomes. Manufacturers recommend reconstitution of products with sterile nonpreserved saline. However, compelling evidence suggests that reconstitution using preserved saline dramatically improves patient comfort without compromising efficacy. Several post-treatment instructions/restrictions are widely used despite the lack of evidence, but muscle activity after injection may be beneficial. Cooling the treatment area might hinder BoNT-A translocation and should probably be abandoned. CONCLUSION: The existing evidence suggests that experienced users should achieve equivalent results regardless of BoNT-A formulation, but additional, well-designed, adequately powered, controlled randomized studies should be performed.

The Use of Botulinum Neurotoxin Type A in Aesthetics: Key Clinical Postulates.

BACKGROUND: The most common aesthetic procedure performed worldwide is the injection of botulinum neurotoxin Type A (BoNT-A). Aesthetic providers must fully comprehend the objective scientific data, theoretical mechanisms of action, and differences between brands of BoNT-A. OBJECTIVE: To determine and review the relevant clinical postulates for the use of botulinum toxin in aesthetics. MATERIALS AND METHODS: The BoNT-A clinical postulates presented here discuss how each brand of BoNT-A acts identically, how the molecular potency may vary between the different products, how patient age, gender, genetics, and muscle mass cause variation in toxin receptor number and density, and how both practitioner and patient can affect toxin distribution. RESULTS: A total of 8 clinical postulates have been identified that are key to understanding the use of botulinum toxin in aesthetics and to obtaining the best clinical results. CONCLUSION: All of these factors affect the potential efficacy of the injected toxin and hence the aesthetic results obtained.

Key Parameters for the Use of AbobotulinumtoxinA in Aesthetics: Onset and Duration.

Time to onset of response and duration of response are key measures of botulinum toxin efficacy that have a considerable influence on patient satisfaction with aesthetic treatment. However, there is no overall accepted definition of efficacy for aesthetic uses of botulinumtoxinA (BoNT-A). Mechanical methods of assessment do not lend themselves to clinical practice and clinicians rely instead on assessment scales such as the Frontalis Activity Measurement Standard, Frontalis Rating Scale, Wrinkle Severity Scale, and Subject Global Assessment Scale, but not all of these have been fully validated. Onset of activity is typically seen within 5 days of injection, but has also been recorded within 12 hours with abobotulinumtoxinA. Duration of effect is more variable, and is influenced by parameters such as muscle mass (including the effects of age and sex) and type of product used. Even when larger muscles are treated with higher doses of BoNT-A, the duration of effect is still shorter than that for smaller muscles. Muscle injection technique, including dilution of the toxin, the volume of solution injected, and the positioning of the injections, can also have an important influence on onset and duration of activity. Comparison of the efficacy of different forms of BoNT-A must be made with the full understanding that the dosing units are not equivalent. Range of equivalence studies for abobotulinumtoxinA (Azzalure; Ipsen Limited, Slough UK/Galderma, Lausanne CH/Dysport, Ipsen Biopharm Limited, Wrexham UK/Galderma LP, Fort Worth, TX) and onabotulinumtoxinA (Botox; Allergan, Parsippany, NJ) have been conducted, and results indicate that the number of units of abobotulinumtoxinA needs to be approximately twice as high as that of onabotulinumtoxinA to achieve the same effect. An appreciation of the potential influence of all of the parameters that influence onset and duration of activity of BoNT-A, along with a thorough understanding of the anatomy of the face and potency of doses, are essential to tailoring treatment to individual patient needs and expectations.

AbobotulinumtoxinA: A 25-Year History.

During the late 1960s and early 1970s, Alan Scott showed that intramuscular injections of botulinum toxin (BoNT) corrected nonaccommodative strabismus without resorting to surgery. The UK doctors who trained with Scott soon realized the significant potential offered by BoNT type A as a therapeutic option for several difficult-to-treat diseases. This led to a collaboration between these pioneering clinicians and the Centre for Applied Microbiology and Research at Porton Down, United Kingdom, and, in turn, to the development and commercialization of abobotulinumtoxinA as Dysport (Dystonia/Porton Down; Ipsen Biopharm Ltd., Wrexham, UK). Dysport was approved in Europe for the treatment of specific dystonias in December 1990 and now has marketing authorizations in 75 countries. Since then, the use of BoNT in therapeutic and aesthetic indications has grown year-on-year, and continues to expand well beyond Scott's initial aim. For example, ongoing trials are assessing potential new indications for BoNT-A, including acne and psoriasis. Furthermore, a growing number of other BoNT products, often termed "biosimilars," together with innovative formulations of well-established BoNT types, are likely to reach the market over the next few years. This review focuses on the history of Dysport to mark the 25th anniversary of its first launch in the United Kingdom.

Recommendations for the best possible use of botulinum neurotoxin type a (Speywood units) for aesthetic applications.

The botulinum neurotoxin (BoNT) product Azzalure (manufactured by Ipsen Biopharm Limited, Wrexham, UK; distributed by Galderma), measured in Speywood units (s.U) has been available since 2009 for temporary improvement in the appearance of moderate to severe glabellar lines. Although we know much about the use of Azzalure for aesthetic indications, some aspects of product use in the clinic still require an update based on continuing and prevailing misconceptions and new clinical data. Therefore, a group of experts experienced with the use of Azzalure convened to formulate the following recommendations: (1) The key to an optimal effect is adequate dosing per injection point. Ten s.U are indicated for strong muscular activity, 5 s.U for medium activity, and approximately 2 s.U for minor activity. (2) The main factor that influences the area of effectiveness is the dosage per injection point. (3) In contrast to former beliefs, we know now that Azzalure works very fast, with some patients reporting initial drug activity after hours. (4) Various volumes can be used for dilution. However, the first choice is the recommended volume, 0.63 mL per vial of 125 s.U. Nevertheless, for clinicians changing products, keeping the volume they are used to might be an option. (5) Clinicians changing products have to be very careful not to confuse the units between different products. (6) In aesthetic BoNT-A usage, the development of antibodies is very rare and is not the common reason for insufficient results. (7) Probably the most common reason when BoNT-A is not working is the absolute or relative underdosage. The present adjunctive recommendations elaborated in an informal expert meeting should help physicians to optimize their treatment with Speywood unit products.

The botulinum toxin LD50 potency assay - another chapter, another mystery.

Observers of the potency assay used for botulinum toxin were greeted last year with the news that one company had an alternative, non-animal alternative in place. But all was not as it seemed from the press release, and over a year later, information is still lacking.

New trends in the science of botulinum toxin-A as applied in dystonia.

New trends and advances in botulinum toxin neuroscience paved the way to the better understanding of the toxin from its behavior at the bench to the clinics. As details of mechanism of action are clarified, we are ready to dispose of product myths, such as diffusion being related to the product being used. Our directions, more precisely on the important subjects such as dose targeting, will translate the science to robust clinical information. Additionally, aspects such as antibody formation, leading to treatment nonresponse, are now understood after long-term treatment series in a variety of dystonic conditions. Avenues leading to combinations of these areas of knowledge will lead to improved botulinum neurotoxin (BoNT) treatment, and further explore the potential of this toxin treatment in association with other treatment modalities, particularly in spasticity and dystonia.

Formulation composition of botulinum toxins in clinical use.

The use of botulinum toxin (BoNT) has now become the treatment of choice for a range of debilitating neuromuscular diseases and for aesthetic medicine. BoNT products are licensed as prescription-only medicines by the health authorities of each country in which they are approved. The authors describe here the current status with regard to BoNT formulations and detail more precisely what is in each product. These data have been presented previously, in a fragmented way, in papers that discuss characteristics of the BoNT products but not the formulations in detail. This information is essential for clinicians in order to enable informed decisions about which products they wish to use clinically. The authors have also examined developments that are either in progress or likely to occur, based on currently available information.

The science and manufacturing behind botulinum neurotoxin type A-ABO in clinical use.

BACKGROUND: Since the first comprehensive description of the physiologic effects of botulism toxicity in the 1820s, specific formulations of botulinum neurotoxin type A (BoNT-A) have been developed. Now, a new botulinum neurotoxin type A formulation (BoNTA-ABO; Dysport [abobotulinumtoxinA]; Medicis Aesthetics, Scottsdale, AZ) has been made available in the United States and these same physiologic effects have become beneficial clinical targets. This formulation has been used successfully for nearly 20 years in Europe and other countries under the trade name Dysport (Clostridium botulinum type A toxin-hemagglutinin complex; Ipsen Biopharm, Wrexham, UK). BoNT-A injections are administered to achieve temporary local flaccid paralysis of targeted muscles. Injection of BoNT-A formulations for aesthetic purposes was by far the most common minimally-invasive (nonsurgical) cosmetic procedure performed in the United States in 2008. OBJECTIVE: The objective of this review is to describe the latest data regarding the mechanism of action of BoNTA-ABO, the potential roles of neurotoxin-associated proteins (NAP), the manufacturing standards for these biologic products, and the specific manufacturing process and characteristics of BoNTA-ABO. METHODS: A systematic search using the US National Library of Medicine PubMed database was performed and the relevant articles were reviewed. Direct input and data from the worldwide manufacturer of Dysport have been included. RESULTS: The four sequential steps in the mechanism of action of BoNTA-ABO are binding, internalization, translocation, and intracellular proteolysis of the target protein. Although all BoNT-A products must meet standards for quality, potency, and safety, they should not be considered equivalent formulations because they have different production strains of the bacterium C botulinum, as well as different isolation and manufacturing processes that result in unique product characteristics. The production steps for Dysport-including a unique proprietary purification process using column chromatography and a unique proprietary finishing process-result in consistent and unique product features. Studies confirm that Dysport has a high degree of long-term batch-to-batch consistency for a range of specified properties, including specific potency, protein composition, toxin complex charge-density properties, and endopeptidase activity. In the native, natural form, NAP protect the endogenous neurotoxin from degradation in the acidic environment of the stomach; in biologic formulations, they may have effects on the structural stability, binding, uptake, and transcytosis of BoNT-A products in other areas of the body. NAP are most likely to stabilize the neurotoxin in a vial of clinical product. CONCLUSIONS: A thorough understanding of the mechanism of action, product characteristics, and effects of NAP is important to ensure appropriate and safe clinical use of BoNT-A products. Now approved in the United States, Dysport is an important addition to the group of available BoNT-A formulations.

The in vivo rat muscle force model is a reliable and clinically relevant test of consistency among botulinum toxin preparations.

To ensure safety and predictable clinical efficacy, the biological activity of type A botulinum toxin (BoNT-A) preparations must remain consistent. Several methods have been employed to assess consistency but lack clinical applicability and/or are associated with animal welfare concerns. Here, we describe a novel in vivo rat muscle force model for evaluating the biological activity of formulated BoNT-A product (Dysport) prepared from bulk toxin batches manufactured at different facilities. Toxin activity was assessed by measuring muscle force generation over time in the triceps surae muscles in the rat hind leg. Animals received 0.1 ml gelatine phosphate buffer (negative vehicle control) or 0.1 or 1.0 LD50 units of BoNT-A in phosphate buffer. Batch equivalence and consistency were confirmed by the lack of significant differences in muscle force generation and duration of effect between each test batch and the reference preparation tested in the same series of experiments. The reduction in muscle force generation was dose-related and reproducible for all active treatment groups. At appropriate dose levels, the rat muscle force model is a reliable tool for measuring biological activity in bulk toxin batches used to formulate clinical product and demonstrates the consistency of batches manufactured over many years.

The Intercostal NMJ Assay: a new alternative to the conventional LD50 assay for the determination of the therapeutic potency of botulinum toxin preparations.

Therapeutic botulinum neurotoxin type A preparations have found an increasing number of clinical uses for a large variety of neuromuscular disorders and dermatological conditions. The accurate determination of potency in the clinical application of botulinum toxins is critical to ensuring clinical efficacy and safety, and is currently achieved by using a lethal dose (LD50) assay in mice. Ethical concerns and operational constraints associated with this assay have prompted the development of alternative assay systems that could potentially lead to its replacement. As one such alternative, we describe the development and evaluation of a novel ex vivo assay (the Intercostal Neuromuscular Junction [NMJ] Assay), which uses substantially fewer animals and addresses ethical concerns associated with the LD50 assay. The assay records the decay of force from electrically-stimulated muscle tissue sections in response to the toxin, and thus combines the important mechanisms of receptor binding, translocation, and the enzymatic action of the toxin molecule. Toxin application leads to a time-related and dose-related reduction in contractile force. A regression model describing the relationship between the applied dose and force decay was determined statistically, and was successfully tested as able to correctly predict the potency of an unknown sample. The tissue sections used were found to be highly reproducible, as determined through the innervation pattern and the localisation of NMJs in situ. Furthermore, the efficacy of the assay protocol to successfully deliver the test sample to the cellular target sites, was critically assessed by using molecular tracer molecules.

Reconstruction of spatially orientated myotubes in vitro using electrospun, parallel microfibre arrays.

The stable culture of myogenic cells and their differentiation into myotubes in vitro is often hindered by the mechanical destabilisation of the spontaneously contractile neotissue formed, resulting in the complete loss of differentiating myotubes. Electrospun, parallel aligned nylon 6/6 microfibre arrays were use successfully for the culture of C2C12 myoblasts and their differentiation to form mechanically stable, orientated myotubes in vitro. Myoblasts adhered strongly to the parallel fibre array, forming a compact cell sheath across the entire array, aligning individual cells in parallel to the direction of the fibrous substratum. The myogenic potential of C2C12 myoblasts was not impaired and resulted in the formation of elongated myotubes expressing alpha-actinin, adult myosin heavy chain and nicotinic acetylcholine receptors as muscle-specific marker proteins. Newly formed C2C12 myotubes were themselves orientated in parallel to the direction of the underlying fibrous substratum and exhibited a high level of structural integration with the surrounding cells. In contrast, non-woven, non-orientated nylon 6/6 meshes, produced by conventional electrospinning, exhibited greatly reduced levels of C2C12 myoblast attachment and adherent myoblasts did not differentiate into myotubes. In conclusion, parallel microfibre arrays provided a superior microscale topography for the stable maintenance and differentiation of myotubes in vitro.