Hyaluronic acid (HA) has been the backbone in the dermal filler market since the 1990’s, prior to this there were a variety of assorted products which have been tried and tested for the same purpose however none have been as successful in what has become the HA revolution.
A Brief History
The concept of non-surgical approaches to cosmetic enhancement came about in the late 1800’s shortly after the invention of the syringe, the very first dermal filler being paraffin. ⁵ This caused considerable issues including granulomas, these are inflammatory nodules which are formed when the immune system recognizes a foreign body and sends in large white blood cells in order clear it. With paraffin such a reaction can occur up to twenty years after the initial procedure. ⁶
Following on from paraffin in the 1950’s the trend was to use injectable Silicone filler fluid, again this had a significant complication rate which exists even to this day even though the use of this product is very restricted. Currently the use of silicone is restricted to specific brands which are highly purified, for specific indications only and for use by specified medical practitioners. However even with these restrictions in place the complication rate is still around 3% and again these reactions can occur after a significant passage of time, occasionally up to as long as fifteen years later. ⁶
After the problems with silicone there was a move towards a more natural animal based product made from collagen but extracted from cattle. This immediately excludes any vegetarians or vegans from utilizing the product and it raises serious concerns regarding immunogenicity. The fundamental issues with injecting collagen is the short duration of action. It is very easily reabsorbed into the body and therefore it has a very short half life. Although it did maintain significant popularity for many years, as previously mentioned the most difficult problem to overcome were the serious issues surrounding hypersensitivity, and even delayed hypersensitivity, in up to 5% of people. ⁷
Finally, the 1990’s heralded the start of the hyaluronic acid revolution as HA was introduced to the market in the mid-nineties.
Hyaluronic Acid (HA)
HA occurs naturally in the body, a human body weighing 60kg will contain approximately 12g in total of HA naturally (0.02%). The natural cellular functions of HA include increasing volume by retaining moisture, increasing cellular integrity and improving mobility and proliferation. ²
The fact that HA is a natural substance already found in the human body signifies a lack of toxicity and immunogenicity and the chance of rejection following implantation is low, although this factor does depend on how the HA is manufactured. For the most part HA is manufactured from microbial fermentation using Streptococcus species (Strep). ⁸ Strep is a pathogenic bacterium and therefore endotoxins are associated with the fermentation end product, this means that a purification process needs to follow. Inevitably there will be some proteins and endotoxins remaining which, if anything, it is this which is going to induce an allergic response.
Hyaluronic acid is a biodegradable polymer that is made up of repeating disaccharide units of N-acetylglucosamine and glucuronic acid which is broken up in the body by a series if enzymatic and non-enzymatic processes. ⁹
The original HA dermal filler was Restylane and this is still in use today although in various incarnations. The optimum concentration for HA is agreed to be approximately 20mg/ml and most fillers are slightly above this now. There are different variations of the same brand depending on the area to be filled.
The original fillers were biphasic, highly elastic, low viscosity, particulate fillers, this gives them a higher potential for migration away from the site of injection. Also, they have a higher potential to be broken up more quickly in the body due to their content of free HA which is much more easily dissolved leading to a shorter duration of action.
The dermal filler REVOLAX is a monophasic, durable smooth gel with unique viscoelasticity, properties meaning it can be expected to hold the shape of the filler where implanted. ¹⁰
Usually Hyaluronic acid has a short half-life in the body however due to the extensive cross linking of the polymer in REVOLAX, this considerably lengthens the time it takes for the product to be broken down. Giving a long lasting durable filler. This combined with the low phase angle of REVOLAX translates into minimal migration away from the site of injection leading to the filler being deposited exactly where it is required, ensuring that the intended look is maintainable for the maximum time frame possible. The particle fillers (like Restylane) have free HA in the filler and are therefore degraded very quickly in the body, lasting between 6-9 months¹¹ whereas REVOLAX the cross linked monophasic smooth gel is more durable and lasts between 12-18 months.
– REVOLAX cross linked monophasic HA gel structure.
The Revolax Family
The entire REVOLAX family contain 24mg/ml of HA making it one of the highest quality products on the market. There are 3 products in the REVOLAX family which all contain lidocaine to make the injection process more comfortable for the client.
This is targets the superficial top dermal layer and is therefore ideal for crow’s feet, forehead lines, neck wrinkles and Glabella lines.
The most popular of the REVOLAX family and targets the mid to deep dermis making it ideal for the naso-labial folds, deeper lines on the forehead, laugh lines, nose and chin augmentation.
The deepest of all of the REVOLAX family this targets the deep sub-cutaneous layer and is ideal for cheek augmentation or where a deeper fill is required.
Having reviewed the available evidence it is clear to see that REVOLAX is leading the way in the HA revolution it is a high quality durable filler which covers the full range of applications. There is an excellent safety record as HA has been in use over a considerable number of years and risk of adverse events is low.
From the research, it is apparent, that for long lasting results which stay true to the original effect the most desired rheological properties are:
- Homogenized gel
- Low phase angle
- Highly Viscoelastic
- High degree of cross linking
- No free HA
All of these are properties of the REVOLAX family of dermal fillers.
Rachel Sawers MPharm MSc MRPharmS | Foxpharma
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