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Transdermal drug delivery

equipment2Transdermal drug delivery

The barrier function of the stratum corneum is vital to protect the skin and underlying structures, but it can serve as a barrier for topical aesthetic treatments. A combination of radiofrequency and ultrasound can help increase skin permeability and allow for topical product penetration, writes Dr Mukta Sachdev

 

We all know that if we can push an active deeper into the dermis, the lower epidermis or the upper dermis, the results are going to be more effective. In an era of evidence-based medicine—it is important to understand the science behind any procedure and have proof of the same. The stratum corneum acts as a barrier and for the past 20 years, many studies have reported that ultrasound can improve the penetration of drugs. In spite of that, we haven’t really understood the mechanism.

Recently, ablative fractional lasers have been shown to increase the skin permeability, following up the laser with a cosmeceutical. We can also use a derma roller and then apply a cosmeceutical. This is trans-epidermal drug delivery.

 

Enhanced delivery

Publications have shown that radiofrequency (RF) creates channels. Topical aminolevulinic acid (ALA) delivery has been enhanced by an erbium laser. Topical 5 -Fluorouracil can be enhanced with lasers as can topical delivery of methotrexate using the erbium YAG laser. Transdermal and trans-epidermal drug delivery is a potential method for enhancing treatment efficacy.

So the new thinking is that the use of these devices can enable us to penetrate the stratum corneum. Cosmeceuticals and topical agents currently in development are using newer technologies, such as nanospheres and different delivery systems. These are designed to enhance delivery and therefore allow products to penetrate deeper into the skin—if we cannot get past the stratum corneum, then it will be difficult to have an enhanced effect.

We need to get to the lower epidermis or the lower dermis to make a difference. The newer treatment , known as the Legato is a combination treatment involving RF to achieve thermal damage followed by an impact technology. We use a unipolar fractional ablative technology, delivering the energy in a fractional manner. When this interacts with the skin, we create a micro-channel.

The RF creates holes are 100–150μm (micrometres) in depth and a width of 80–120μm.

 

Micro-channels 

When we have an open microchannel and apply a topical drug, we have a better chance of penetration. We can use an ultrasound technology and push the drug into the epidermis. Looking at this theoretically, it makes a lot of sense.

We’ve made a channel and whether we push hydroquinone, topical retinoic acid or hyaluronic acid, the product is getting deeper and having some effect. The ultrasound works through a thermal, cavitational and an acoustic streaming effect. High acoustic pressure and sonophoresis help force the product down.

I use the Alma Legato, which has a sonotrode which tends to improve product distribution under the skin. While the science behind this delivery works, we have to be careful of the active we’re using. None of the actives which have been developed or studied are meant for intradermal use.

For example, mesotherapy products have not been developed for intra-dermal use. But, as far as I can foresee, the only possible complication would be a potential reaction to the vehicle of the topical.

But if we’re performing any kind of mesotherapy or derma roller, we’re already providing a form of transepidermal delivery. The only difference is when you use a device such as a laser—we’re then providing controlled, reproducible results.

 

Indications 

With this technology, we can target anti-ageing, rejuvenation, scars and stretch marks. I find the treatment most beneficial for stretch marks— we see good results. Medicines used include glycolics, hyaluronics, Vitamin C, hydroquinone and kojic acid. We’ve also used peptides; any of the active topicals that you would prefer in a particular indication can be used.

During the procedure, there is some amount of burning sensation—it is an RF treatment after all. We use topical anaesthesia for at least 45 minutes because they can’t tolerate the pain of the RF. The pain progressively reduces over 12 hours. Once you apply the topical and you’re using the ultrasound probe, the patients tend to say they feel better.

The whole treatment takes around 15–20 minutes. We can see significant erythema which looks really painful, but it’s not usually as bad as it looks. Patients tend to have three to four days of downtime following the procedure.

For stretch marks, we’re looking at around a 30–40% improvement. If we look at the underlying aetiology of striae, the skin has been stretched, torn and damaged. We can’t repair the whole thing, but we can improve the appearance.

We can also use the treatment for acne scars. It can provide a good improvement in the texture on the face. New scars show better improvement than old scars. In general, we aim for a 20–30% improvement for scarring.

Melasma will improve temporarily—it’s not a permanent treatment for melasma. But it’s an adjunctive treatment for melasma; the condition is dynamic and does come back. But this technique can be used as an adjunctive therapy.

Trans-epidermal delivery is kickstarting a new generation of treatment devices in dermatology, focused on combination therapies. We want to combine procedures and topicals for more effective results.

Dr Mukta Sachdev is a professor of dermatology and practising senior consultant dermatologist and runs her own dermatology consulting firm. She specialises in lasers and aesthetic dermatology in skin of colour

 

Author: bodylanguage

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