It has recently come to my attention that there is STILL a lot of misinformation regarding Botulinum Toxins being propagated by supposed “experts” in the field of aesthetics. Hence the decision to get the latest and up-to-date scientific-based evidence regarding what has been the most popular non-invasive cosmetic procedure requested and carried out worldwide.


Since its molecular discovery in the 1820´s, Botulinum toxin has been used as early as the 1950´s for its therapeutic muscle relaxation properties (especially following nerve damage, strokes, strabismus and even bladder overactivity). The cosmetic potential was initially documented by Dr Carruthers, a Canadian Ophthalmologist in the 1980’s who noticed a reduction of eye wrinkles in patients being treated with this neurotoxin for blepharospasm. Around the same time the pharmaceutical company, Allergan, patented the name “BOTOX” … and the rest is history. Currently, the main manufactured brands are: Botox®/Vistabel® (OnabotulinumntoxinA; Allergan Inc., Irvine, CA, USA), Dysport®/Azzalure® (AbobotulinumtoxinA; Ipsen, Slough, UK/Galderma, Paris, France), and Xeomin®/Bocouture® (IncobotulinumtoxinA; Merz Pharmaceuticals GmbH, Frankfurt, Germany). All of the above brands are FDA approved and widely available in Europe. In Portugal, they are all available from specific pharmacies on prescription only, or through clinics registered with Infarmed (the national pharmaceutical controlling authority).

There are other brands also available in the namely: the newly approved Jeuveau (PrabotulinumtoxinA), Neuronox and Botulax in South Korea, Relatox in Russia, and the Chinese Chinatox/CBTX‐A which is also marketed internationally under a variety of names including Prosigne, Lantox, Liftox, and Redux. Plus several new products still under research and development: daxibotulinumtoxinA (DAXI) and nivobotulinumtoxinA (NIVO), marketed as Innotox in South Korea.


All neurotoxins approved for aesthetic use are derived from the Hall strain of Clostridium botulinum type A. There are 6 other Botulinum toxins: types A, B, E and rarely F, cause human botulism, while types C, D and E cause illness in other mammals, birds and fish.

These neurotoxins work by binding to the surface of the nerve endings’ end-plate, basically creating an “insulating” layer preventing the neuronal impulse reaching the muscle and causing it to contract, thus leaving the muscle in its relaxed state. Since muscle contractions create the formation of skin folds and wrinkles, relaxing the muscle smooths out the overlying skin. This is a very simplified version of a rather complex chemical reaction which scientists are still learning to understand completely. The neurotoxin appears to bind to the nerve end-plate permanently, however, through as yet poorly understood metabolic processes of toxin breakdown as well as the ability of the nerve endings to “sprout” new end-plates, the “relaxing” effect wears off and themuscle is able to contract again. The onset of action starts around 48 hours following injection and can last 3-5 months.

And this is where the drama and the controversy begins … with each manufacturer claiming their product is superior to their competitors in term of efficacy and longevity.
The manufacturing process of each commercial neurotoxin is similar but is product unique in terms of toxin purification, excipient addition, preparation and finally finishing and drying… not to mention transport, storage and reconstitution of the product, all of which can affect its efficacy and longevity. However, researchers have stated, “ … None of the methods investigated for measuring or quantifying longevity give a good standard, as there is no consensus on what is ‘effective’, nor a quantifiable, reproducible method by which to measure it…” thus clinical data has not always supported manufacturer’s claims.

The maximum clinical effect has always been the “frozen“ look, with the higher degree of frozenness correlating to a greater longevity (although also increasing the potential for adverse effects), however, many patients prefer a more natural look with some facial movements being maintained, making evaluation more difficult. Added to this, there are no adequately formulated studies comparing each product directly, as split face studies can only compare 2 products at a time, and animal studies do not always correlate exactly to human muscle function.

Claims and counterclaims in advertising campaigns have even led to legal action in the UK between Allergan and Merz in 2011, with Merz claiming Allergan did not have any scientific basis to claim their product was superior, a claim which was awarded to Merz.
This inexactness of clinical data led to The Eight Key Clinical Postulates by Nestor et al, being published in 2017 and updated in 2020, as a guide for the aesthetic practitioner to understand and compare the properties and characteristics of all available Botulinum Toxin products.

In a nutshell the key points of the document state that:
1) all Botulinum Toxins type A act identically.
2) efficacy and longevity of product is determined by not only molecular potency but also patient characteristics such as age, gender, ethnicity, skin type and actual muscle mass.
3) molecular potency of each commercially available product is very difficult to quantify objectively and no clear data exists to date to show statistically significant superiority of one pro
duct over another
4) efficacy and longevity can further be affected by diffusion of product which is affected by product reconstitution, dosage, injection technique, and number of injections, which are tailored to each individual.
So these are the expert findings, now make sure that you find the right expert too before you decide to tox or not to tox.

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