Not your Grandma’s Botox.

Despite the relatively novel study of botulinum neurotoxins in the field of science and even more so their cosmetic application, the term Botox has rapidly gained notoriety among the general public for its remarkable effectiveness, seemingly miraculous applications, and real and perceived dangers. Yet publications reviewing its background, development, and growing uses are relatively few, though growing, even with it being the most popular cosmetic procedure in the United States with more than 6.6 million injections of botulinum toxin type A (BTA) in 2014 alone. Much like the discovery of its cosmetic uses, the history of botulinum toxins is a colourful and often unexpected one, from its emergence to today.

Sausage Poison: Taxonomy | Physiology | Pharmacology

Around 1820, Justinus Kerner, German poet, physician and medical writer, observed that the botulinum toxin tended to thrive in poorly-prepared meat products and gave it the moniker “sausage poison”. About half a century later, it was translated into the latin “botulus”, meaning casing or sausage, and thus the disease it produced was named (Article 1). Botulinum neurotoxins are produced by Clostridium botulinum, an anaerobic, Gram + ve, spore forming bacillus which produces a potent, neurologically directed exotoxin. Based on the antigenic specificity of each exotoxin, there are eight serological types (A, B, C1, C2, D, E, F and G) with types A (BTA) and B (BTB) commercially produced for clinical use. While BTA and BTB have similar functions, they are antigenically different, allowing those few who have developed antibodies to still benefit from neurotoxin treatment. 

All serological types share amino acid sequential, structural, and functional commonalities acting on the different parts of the same target receptor, with the exception of C2 which is not a neurotoxin. Biochemically, the botilunum toxin is synthesised at the molecular weight of 150 kDa and the polypeptide comprises 2 chains: one light (50 kDa) and one heavy (100 kDa) conjoined by a disulphide bond, which is disrupted upon toxin activation. Interestingly, although very similar to tetanus, botulinum toxins exert the diametrically opposite effect of a flaccid paralysis, contrary to the muscle stiffness and spasm that prompted the lay term ‘lockjaw’ for tetanus (Article 1)

From Bioterrorism to Rejuvenation

Prior to its refinement for cosmetic applications, the causative bacterium Clostridium botulinum was first cultured by Belgian bacteriologist Émile van Ermengem in 1897, eventually leading to the emergence of it’s application as a neuromuscular blockade agent in 1949. The potential role of the botulinum neurotoxin A (BoNT-A) as a bioterrorism agent has been explored by several governments, including those of Japan and the United States (Article 4), and it is rumoured that Gestapo commander Reinhard Heydrich lost his life to a BoNT-A containing grenade (Article 1). It is also rumoured that Fidel Castro successfully thwarted a BoNT-A attack by the CIA who attempted an assassination by reputedly impregnating a box of his favourite Cohiba cigars with the toxin. It is estimated that a single gram dose of BoNT-A, when inhaled, is sufficient to kill one million people.

It is important to note, however, that BoNT-A – the serotype most frequently used for cosmetic purposes – has largely different consequences when injected into the skin, and that a standard vial has 2 x 10-8, or 200 million times less mass than a lethal dose. The first clinical uses of BoNT-A were reported in the 1970’s as approved its use for the treatment of facial spasmodic disorders. The same year, surgeons Clark aa non-surgical alternative for strabismus, selectively weakening the extraocular muscles. It went on to be used as a selective depressor of skeletal muscle activity for other ailments such as blepharospasm, hemifacial spasm, and in 1989 the FDA nd Berris used the treatment to correct facial asymmetry resulting from iatrogenic facial nerve damage during rhytidectomy, and while this is widely considered the first aesthetic use of the botulinum neurotoxin, that claim remains contentious.

Many consider the true pioneers of cosmetic application of BoNT-A to be wife and husband team opthamologist Jean Carruthers and dermatologist Alastair Carruthers. While getting treated for blepharospasm, a patient noticed improvement in the wrinkles of her periorbital region and requested to have her forehead injected as well. Knowing that her husband also had patients seeking improvements for facial rhytides, in an epiphanous connection Jean Carruthers injected the glabellar frown lines of her willing receptionist, and with their preliminary successes the aesthetic use of BTA was born. This led to  further experimentation culminating in a report published in 1992 that set the stage for the development of Botox Cosmetic and several other products marketed specifically for aesthetic use. However, the Food and Drug Administration (FDA) approval for the cosmetic use of “Botox” only came in April 2002, but was  limited to the glabellar area. It has since been approved for other cosmetic indications such as forehead lines and crow’s feet.  It is important to note that all other areas are treated in an “off-label” manner.

Beyond Botox

At this time there are 4 commonly used preparations of botulinum toxin: onabotulinumtoxinA (Botox; Botox Cosmetic, Allergan, Irvine, CA), abobotulinumtoxinA (Dysport; Ipsen, Ltd, Berkshire, UK), incobotulinumtoxinA (Xeomin; Merz Pharmaceuticals, Frankfurt, Germany), and prabotulinumtoxinA (Nuceiva; Evolus, San Francisco, CA). Although the clinical effect of each is similar, they differ in their chemical structure, associated proteins, manufacturing and purification processes, mechanism of action, and clinical efficacy. While America is predominantly Botox territory, and being first to market it bullishly popularised the commercial name, Europe has had the UK manufactured Dysport for almost as long. A more recent entrant to the market labelled Xeomin from Germany had been thought to have no complexing proteins. Initially it was believed these played a distinguishing role, but it is now known that dissociation is virtually instantaneous at physiological pH so a reduced protein load is only a theoretical advantage. Nuceiva is the most recently approved preparation in Canada and the US and is said to be bio-identical to Botox, the only difference being the manufacturing process. In essence, all share the 150 kDa neurotoxin, but have different associated proteins. Because of these differences as well as commercial, proprietary secrecy, there are no established dosing equivalencies between products, although some general clinical guidelines have emerged. Most experienced BTA injectors use the following BTA dose conversions for aesthetic facial uses: 1 unit of onabotulinumtoxinA = 1 unit of incobotulinumtoxinA = 1 unit of prabotulinumtoxinA = 3 units of abobotulinumtoxinA.

Aesthetic Treatment (and Mistreatment)

The science behind BoNT-A treatment is relatively straightforward; injection targets the hyperkinetic muscles beneath wrinkles. As the toxin defuses, through attachment of the heavy chain, it binds to the axon terminal surface – a process that takes approximately 30 minutes. Once the heavy chain is attached, the light chain passes through the channel formed as the disulphide bond weakens, specifically degrading cytosolic soluble N-ethylmaleimide-sensitive fusion-attachment protein-25 (SNAP). The following process of acetylcholine release from the presynaptic terminal of the neuromuscular junction takes time, which is why results take about 2-3 days to become evident, and are also dose dependent, with the peak effect occurring between 5-8 days, but can take as long as 14 days.  Because of the synaptic switching and neurogenic axonal sprouting that occurs, the effect wears off after about 3-6 months. The percentages of patients maintaining a clinical response after three months of treatment was found to be approximately 60% for Nuceiva,  50% for Botox, 40%-50% for Dysport, and 15%-25% for Xeomin, although that last statistic may likely be skewed due to a 2-point vs 1-point measurement of clinical improvement. However, benefits have also been observed to increase over time, leading to a diminished production of wrinkles due to a conditioning created by regular injections (and therefore correspondingly allowing longer intervals between treatments). 

Though the wearing off of BoNT-A treatment over time can be irksome to the patient, it also offers the saving grace that any adverse effects will wear off over time as well. Most adverse effects can be attributed to predictable issues such as unwanted or excess effects of the neurotoxin as caused by a combination of factors; patient behaviour (receiving treatment from more than one practitioner or irregular follow-up), and faulty physician practices (injection technique, dosing, and frequency of administration) being the main two. A good functional knowledge of facial muscle anatomy from the practitioner is certainly required, though accurate determination of therapy failure is difficult due to the lack of standardisation of doses and technique. The upper face, and the aforementioned glabellar region, experience the best results from BoNT-A treatment as the area sees less volume loss with age, and the most evident signs of ageing are related to rhytides. Moreover, recent studies show that the treatment of glabellar rhytides can improve quality of life and reduce negative moods. BoNT-A treatment of the mid and lower face can be slightly less effective due to volume loss in the region, though there are many examples and incidences where chemodenervation of these muscles can reduce downward pull, provide a subtle lifting effect, and soften rhytides producing desirable effects. 

Another effect which may be considered adverse is an antibody-mediated immune response in the patient that causes them to become immune to further injections, though this is not very common according to recent studies, especially in cosmetic practice as the doses are very low. Localised adverse effects can include bruising, which is why it is important to use the smallest needle possible, and headache in the initial 24 hours. Blepharoptosis is also often cited, but simply refers to a spread of the effect beyond that intended, causing a drooping of the eyelid. The diffusion upon injection responsible for the effect can be avoided by careful technique involving digital pressure on the orbital rim, as well as avoiding post-injection massage. There is also some evidence that Dysport diffuses more than Botox, and that using an ultra-concentrated technique and/or lower volume, can help.

The FDA reviewed all serious adverse events  between 1989 and 2003 and reported a death toll of 28, 4 of them children. None of the deaths, however, occurred in cosmetic uses and 26 were determined to have some underlying systemic disease carrying an elevated risk of mortality. Another fatality was recorded from a presumed anaphylactic reaction to off-label BoNT-A use for neck pain. As can be predicted, the most adverse events have been reported from unlicensed, ‘black-market’ preparations and unscrupulous practitioners, with one distressing case in 2004 where a suspended Floridian doctor by the name of Bath McBomb injected patients, his girlfriend and himself with a non-approved illegal formulation containing as much as 10 million Botox Units (BU) as opposed to the standard vial of 100 BU. They were lucky to survive the systemic botulism that resulted in their artificial ventilation. It bears to mention again that no deaths have occured from cosmetic procedures, and the risk will continue to be minimal with reliable practitioners practising individual patient assessment, careful injection site selection and proper injection techniques, dosing, and follow-up.

Tox out of the Box

Moving beyond the realm of cosmetic application, the positive, therapeutic applications of neurotoxins and specifically BoNT-A continues to grow. In October of 2010, the FDA approved its use for the treatment of migraine-type headaches. As mentioned, with the correction of glabellar lines, an avenue of research has found antidepressant effects through the reverse engineering of emotions; based upon the hypothesis that the brain is constantly aware of what the body is doing, through continuous feedback, a lack of frown can possibly turn your mood upside down. A Californian surgeon has claimed a link between BoNT-A injection and baldness; combining it with a cocktail of vitamins, he has found that the improved circulation through reduced scalp muscle tension stimulated hair cell growth. While this last technique requires further study and testing, it is a promising sign that with proper use, botulinum neurotoxins, as seen throughout their varied and surprising history, offer many benefits to humans, cosmetic and beyond. 

References

M.G. Berry, M.G. & Stanek, Jan J. (2012). Botulinum neurotoxin A: A review. Review | Volume 65, Issue 10, P1283-1291. https://doi.org/10.1016/j.bjps.2012.04.016 

Gart, Michael & Gutowski, Karol. (2016). Overview of Botulinum Toxins for Aesthetic Uses. Clinics in Plastic Surgery. 43. 10.1016/j.cps.2016.03.003.

Arnon SS, Schechter R, Inglesby TV, et al. Botulinum toxin as a biological weapon: medical and public health management. JAMA 2001;285:1059e70.

Clark RP, Berris CE. Botulinum toxin: a treatment for facial asymmetry caused by facial nerve paralysis. Plast Reconstr Surg. 2005 Feb;115(2):573-4. doi: 10.1097/01.prs.0000150149.74749.55. PMID: 15692366.