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| My hesitation grew even more when I started researching transdermal absorption. On this page you'll find what I was uncertain about - and what I discovered. But first, let's name some facts. |
What is transdermal absorption
"Transdermal" literally means "through the skin".
Transdermal absorption is the process wherein a substance (usually a drug, or supplement, like vitamin B12) enters your body directly via the skin.
Sounds very simple. You put a cream, or gel, or vitamin patch on your skin - and voila! You get all the active elements delivered into your bloodstream.
Not so quick.
The main purpose of your skin, which is the largest organ of the human body, is to protect you, and not to let foreign particles into your body. Very few substances can get through the skin (the technical term for this is low permeability of the skin). Skin consists of several layers of different kinds of cells, and each layer contributes to the ultimate high resistance to external substances.
Mucosal tissue - a "wet" surface inside your mouth and nose, for example - is less resistant than skin, but it is also not very "transparent" to drugs and supplements.
As described on the page about spray vitamins, there are three major qualities which determine how easily a substance can be absorbed through mucosal tissues:
- Fat-like (dissolving in fats) drugs have more chances that water-like (soluble in water) drugs
- Smaller molecules penetrate more easily than larger ones. Some sources give the number of 1000, others - 500, as the highest molecule weight for a reasonable absorption rate via tissues like oral mucosa.
- Neutral molecules penetrate through mucosa better that ions (charged molecules)
The same criteria are true for skin.
So, what are the chances that vitamin B12 can be absorbed through your skin?
Based on the above three factors alone - not very good.
Molecules of vitamin B12 are neutral - but this vitamin is water-soluble, and has the largest molecular weight of all vitamins (about 1357). This means it cannot be easily absorbed through membranes like oral mucosa - or skin.
Yes, it is absorbed sublingually (refer to the spray vitamins page), but the absorption rate is about the same as when you take B12 orally (i.e., swallow it).
If a substance is not absorbed better through a thin oral tissue - what can you expect when it is applied to your skin?
Let's not arrive at a final conclusion yet.
Benefits of transdermal absorption
There are about 30 or so different drugs which are available in the form of patches, per this article.
Remember the molecular weight of 500-1000 as the upper limit for a good absorption?
Here are some numbers for medications used in a form of skin patches:
- Nitroglycerin - 227
- Fentanyl - 336
- Nicotine - 162
- Estradiol - 272
- Testosterone - 288
I just picked the names of fairly known drugs that I recognized, or those with larger market shares among TDD (Trans Dermal Delivery) drugs.
Have you noticed? All the numbers are less than 500, and far less than the molecular weight of vitamin B12! (Oh-uh, I become suspicious more and more about those B12 patches...)
But let's get back to the transdermal absorption.
There are several reasons to believe that transdermal delivery may be preferable to oral delivery for a large number of patients.
- First, delivery via the skin can potentially improve patient compliance compared with oral delivery. With patches, there are no restrictions regarding the time that a drug must be taken, or what you can/cannot eat, or drink before/after taking it. Need to take medicine for several days? Put on a patch, and "forget about forgetting" to take a drug at a specific time!
- There can be also the advantage of higher bioavailability, compared to the oral route, which means that smaller doses may be used for the same drug, helping to minimize side effects.
- When you use patches, a substance from the patch is delivered directly into your bloodstream - bypassing the gastrointestinal (GI) tract. This can help people with digestion or metabolism problems.
- To bypass GI tract, you can take a drug in form of shots. Vitamin B12 shots are often prescribed to patients with b12 deficiency, and who have digestion or metabolism problems. But let's agree: patches are much more easy to use - and there is no pain, besides...
- Finally, if any adverse side effects occure - you can stop drug delivery immediately by removing a patch. Not so if a drug was swallowed, or injected.
All this is good news - but what about those doubts of mine?
I mean - what about the ability of vitamin B12 to go through your skin?
Transdermal absorption of vitamin B12
I discovered an article written in March 2004, where a company called Dermatrends® is mentioned.
This privately held firm developed a patch which seemed to overcome problems with the skin's resistance to drug delivery. They developed and patented so-called "permeation enhancer": a chemical which makes skin less resistant to external molecules. They even reported that it does not irritates the skin too much.
And here is the best part:
this enhancer works for substances with molecular weights... up to 1380.
Why do I call this the best part?
Because this means that this patch will work with vitamin B12 on it!
It might be that developing a B12 patch was the goal of that research, because the same article reports on a successful [transdermal] delivery of vitamin B12.
Here is a link to the article for your reference.
Hmm...
I spent quite a lot of time searching for information about B12 absorption, and this was the only source with some real information: company name, method, test results. It was dated March 2004.
I checked archived historical pages from a website of the company that produces and sells vitamin B12 patch. The first time their homepage appears with information about B12 patches in March 2006.
Assuming these two companies are related (I could not find more information sources, right?), the period of two years from a successful test to production seems a reasonable amount of time.
I don't know about you, but this last discovery somehow gave me some relief, and my doubts disappeared almost completely.
Why only "almost"?..
Well, I guess I will need to try this vitamin B12 patch on myself to be fully assured... :-)
