Topical vs Transdermal Administration
What's the difference?
Topical vs Transdermal Administration: What's the difference?
by Dr Linda Klumpers
It is not surprising that people often get confused when hearing the words topical and transdermal, because we regularly see these terms used incorrectly in the media, in the industry, and even on products themselves. After reading this text, you will have learned what the differences are, for good.
Topical. Topography. Topology. These words sound similar because they share the same root derived from the ancient Greek word topos (τόπος) meaning place or location. Topical administration is a local administration that acts at the location where it is administered. It might sound logical at first but think about swallowing a painkiller when you have a headache: the painkiller is not supposed to work in your mouth or your gastrointestinal tract, but more around your head. Topical products can be administered at various places on or in the body, such as the mucosa or the eyes, but when it comes to cannabidiol (CBD) products, we mostly use them on the skin. Weighing more than 20 pounds (around 10kg), the skin is our largest organ that is the easiest to access. (Leider, 1949)
The better and the longer you rub in your topical product, the more efficiently it will penetrate the tough outer layer of the skin, see figure 1.
Transdermal is also derived from ancient Greek and means through the skin. As opposed to the topical (local) administration that remains on the place of application, a transdermal product moves through the skin layers and ends up in the blood vessels of the lower skin layer. From the blood vessels, the transdermal compounds can travel through the whole body, just like with oral administration or inhalation, and end up in various organs, such as the brain. In figure 1, you can see which skin layers transdermal compounds travel through. How deep a product will go depends on various factors, among which is the thickness of the skin that varies between different body parts. That is why labels contain instructions on where to apply a product for the best results.
Why use topical products?
If topical products do not move through the body and do not get widely distributed to other organs, why use them? There are many uses for topical products, and many people apply them daily. Just think of cosmetic products, such as make-up and fragrances; creams and balms for dry hands, feet, or lips; shampoos for the sensitive scalp; sunscreen as a protection against UV radiation (cannabinoids are good at absorbing sunlight! (Hazekamp et al., 2005)); lubricants for vaginal or rectal application; gels for a cooling or warming sensation; medication for skin disorders such as eczema and psoriasis, etc.
Why use transdermal products?
Most products that are applied to the skin are topical products. After all, the main function of your skin is to protect you from the outside world, so merely applying a compound does not make it enter your body. Just think of swimming in chlorinated water for hours: if it were not for your skin and your swimming skills, you could not survive a swimming pool. To get compounds to travel through your skin and reach your bloodstream, formulation chemists need to apply special tricks. These involve moving the compounds via pores in your skin, such as sweat ducts, enabling them to penetrate straight through your skin cells, or make them ‘zig-zag’ around your cells through the skin to its deep layer. (Ng and Lau, 2015) For each method, different product properties are required.
Why would you want to use transdermal products? After all, if a transdermal route can get compounds into your blood just like oral or inhalation routes can, why bother applying a product to your skin? Simply put, the characteristics of transdermal products can be quite different from those of other product options. Think of inhalation: after you inhale a product, you feel the effect within minutes, and after a few hours, the effect is gone. Transdermal options are generally designed to continuously give off a small portion of compounds over a long period, allowing the effect to last for hours while avoiding variable high and low effects. This can be desirable for effects that you want to have present consistently throughout the whole day, such as with nicotine patches against tobacco use.
Another reason for using transdermal compounds is that it increases compliance: if you need to take a daily contraceptive pill, the consequences of forgetting one can be significant. With a contraceptive patch that you apply once a week, the risk of forgetting your contraceptive decreases by a lot.
How to tell the difference between topical and transdermal products in a store?
If you are wondering how to easily distinguish topical products from transdermal ones, you cannot! Both topical and transdermal products come as creams, gels, lotions, patches, salves, etc. The best thing you can do is look on the product label: does it say topical or transdermal?
Sometimes, however, product companies give wrong information, and you can occasionally come across administration methods that contradict product descriptions. One example that we have found recently is a cannabis product manufactured by a relatively big cannabis company. The product contains 60mg of the intoxicating (feeling ‘high’-inducing) compound THC, which is a lot, considering that THC-containing products in Oregon should be divisible into doses of 5mg. Yet, the manufacturer claims that full absorption of the product will not lead to feeling high. If companies advertise that their transdermal cannabinoids will give no psychoactive effects, such as in this case, you can rest assured that there is something wrong with their products. It is most likely that the products are not really transdermal but only work locally.
As you have learned from the text so far, topical and transdermal products have very different functions and applications. One is not better than the other, as it all depends on why you want to use a product.
Does Green Earth Medicinals have topical or transdermal products?
Green Earth Medicinals carries a variety of topical creams and liniments: CBD RELIEF Cream, CBD RELIEF Muscle Spray, and CBD RELIEF Roll-on (Figure 2). No matter the container your product comes in, it is important to rub the product into the skin well, be it topical or transdermal. This allows the product to get deeper into the skin and prevents the product from being easily washed off or wiped away by clothes. Green Earth Medicinals does not carry transdermal products, which means that their products do not have so-called systemic side effects such as drug-drug interactions, nor do they show up in urine drug tests. Green Earth Medicinals products come in various forms and with various terpene blends, which means that every product has its unique smell.
- Topical products act locally.
- Transdermal products act systemically (throughout the body) and can act on all your organs, including your brain.
- The only way to distinguish topical and transdermal products is to read the product label.
- Rubbing topical and transdermal products on the skin generally gives better results.
- Green Earth Medicinals carries topical products.
We are now working with our friends at Cannify to bring you more information on important topics. Cannify researches and educates about cannabis. It is the first company to match patients and products with science. Cannify's founder Dr. Linda Klumpers earned a Ph.D. in Clinical Pharmacology of cannabis and has been studying cannabis for over a decade. Cannify educates an audience that includes patients, healthcare providers, and university students, and is actively involved in various cannabis-related research projects.
- Hazekamp, A., Peltenburg, A., Verpoorte, R., & Giroud, C. (2005). Chromatographic and spectroscopic data of cannabinoids from Cannabis sativa L. Journal of liquid chromatography & related technologies, 28(15), 2361-2382.
- Leider, M. (1949). On the weight of the skin. Journal of Investigative Dermatology, 12(3), 187-191.
- Ng, K. W., & Lau, W. M. (2015). Skin deep: the basics of human skin structure and drug penetration. In Percutaneous penetration enhancers chemical methods in penetration enhancement (pp. 3-11). Springer, Berlin, Heidelberg.