Trans Dermal Delivery System
Updated Mar. 21st, 2022
Trans dermal delivery involves the absorption of medicinals, nutraceuticals, now even cosmoceuticals and aromatherapy, via patch or liquid (gel, cream, etc) applied directly to the skin. The substance then travels through the outermost layers of skin to the highly vascular dermis layer and subcutaneous tissue, where it enters the bloodstream and exerts its medicinal action. Some systems even claim to bypass these deeper layers penetrating the muscle layer below.
This absorption through the skin can happen intracellular (between the cells), through transcellular absorption (across the cells), or via transappendageal penetration, which occurs at hair follicles, and sweat and sebum glands.
Popular Uses
Whether you realize it or not, you are probably familiar with a few well-known examples of transdermal delivery systems. The nicotine patch is the highest selling transdermal patch in North America. It releases nicotine in small, controlled doses through the dermis (skin) to help with smoking cessation. Hormonal patches have also increased in popularity. Estrogen patches for the treatment of menopausal symptoms, contraceptive patches for birth control, and testosterone patches for both men and women, are a few examples. Opiod patches for severe pain relief are also available.
Transdermal versus Oral delivery
What’s the liver got to do with it?
A first pass effect occurs when an orally administered substance travels to the liver where it is filtered before it is enters the blood stream and is sent out to the applicable areas/cells of the body. Substances with a high first pass effect are more highly filtered when passing through the liver. There is significantly less medicinal property/active property left once the liver is finished with it. With transdermal delivery, these substances can bypass the liver to get into the vascular system and cells without being compromised, meaning less is needed for a much more effective outcome.
Compromised digestion
As we age, our digestive system, particularly enzymatic reactions that breakdown molecules to allow for easy and effective digestion and absorption of nutrients or medicines, slows down. As such, the older generation, and perhaps the most medicated and in need of nutritional support through supplementation, aren’t always able to take advantage of orally administered substances. Again, transdermal administration bypasses the digestive system completely. This is also of benefit to those with conditions such as IBS, Crohns, and Colitis. In these cases, intestinal permeability is compromised and absorption of medicines of supplements through the gastrointestinal system is significantly impaired.
Other benefits:
- Transdermal delivery, as in the nicotine patch, also allows for a controlled release of medication into the system.
- Transdermal delivery is less invasive than parenteral/IV therapy
- Transdermal delivery may only require once daily (sometimes once weekly or monthly) dosing/administration = Ease of use.
- This also creates better patient compliance.
The problem is…
The problem with transdermal delivery systems is that only certain types of substances, more specifically, smaller molecules with the ability to diffuse into skin lipids, can pass through the skin for direct absorption into the bloodstream.
An effective barrier!
The skin is actually an extremely effective barrier system (If it weren’t, we’d be in a lot of trouble!). As such, only small molecules that will effectively diffuse into skin lipids can effectively pass. The challenge is to allow for better penetration through the thick stratum corneum layer of the epidermis (the outermost layer of the skin) without modifying the medicinal substance itself. Drug manufacturers attempt to do this by pairing these medicines with a substance that will change the skin, instead; altering the physicochemical properties of the stratum corneum, the structure of the lipids and lipoproteins in the cellular channels, and increasing hydration. When this is not possible, or further help is necessary, they design a carrier mechanism to literally transport the drug across these first layers. Studies using an applied electrical field (iontophoresis) or high frequency ultrasound are also showing promising results and may enable larger molecules to pass.
A few more hurdles
These delivery systems are also, at this time, reserved for more potent medications. This way only a small amount of the substance is needed, as well as these substances being a better match for the skin’s impermeability.
The location of the patch (where the patch is administered on the body) must also be changed regularly to avoid irritation.
Similarly, substances that are irritating to the skin, or sensitize the skin cannot be used.
There are advancements made everyday in the field of transdermal delivery and in the not so distant future, I believe more transdermal delivery options, both in the field of natural substances and pharmaceutical medications, will be widely available.
Stay tuned!