TL:DR - highly plausible, worth trying.
Transdermal: simply, application and absorption of a drug onto the skin. Transdermal is nothing new in medicine, starting out in the late 70s, while 'TD' testosterone has been around since the 90s as a patch, and the gels became available at some point in the 2000’s. Full list of all currently FDA approved TD drugs available here. Interesting list of those in development available here.
In the case of TD test, it has a bioavailability of 10%, compared to testosterone administered by injection which has a bioavailability of 95%. This is because one of the biggest issues in TD delivery is that the skin itself is meant to keep foreign objects like chemicals out of the body where as if you can deposit it into fat (subq) or muscle (IM) the compound is far more bioavailable.
TD advantages seem obvious: no (scary) needles, reduced impact on liver and other organs, and reducing initial metabolization of the compound. However, Successful transdermal delivery is based on achieving a suitable balance between effective delivery and safety to the skin. That’s key, because enhancing chemically the delivery of the drug has a proportional effect on the skin, such as irritation. And you can’t apply a compound to your armpits when your skin is screaming from weeks of application.
So what determines if a compound can be used TD? Basically, its ability to penetrate the initial layer of the skin. There does not seem to be a limit on which compounds can do this, at least not that I could find. The FDA approved TD drugs have a wide variation in chemical formula and weight:
- Scopolamine is 303.353 g/mol
- Nitroglycerin is 227.0865 g/mol
- Testosterone is 288.42 g/mol
- Oxybutynin is 393.952 g/mol
For reference, penicillin is 334.39 g/mol.
With such a wide variance, it gives me hope... LGD4033 is at 338.253 g/mol, similar to other compounds we know can be applied TD. And the kicker is that there are already suppliers selling TD variations of LGD4033, so I’m optimistic because we all know that suppliers of illicit compounds would never lie or sell bad products.
Of course, there’s no trials of transdermal LGD4033, or any of the other common SARMs in a TD application that we use within the /r/PEDs community. But it’s not that far out a concept, and it seems like there is little risk.
Google searching ‘how to make a transdermal’ led me into a world where this is common in Mary J (ofc... anything to get high), as well as broscientists who have came before us. DMSO apparently works as a carrier, as does a solution of benzyl alcohol, acetone and isopropanol. While I will steer off linking those pages since they are marketplaces, they were easy to find. Determining a formula would be the next item to solve for, and with bioavailability of LY305 at about 10% and testosterone also being 10% it seems to me that it would be a good place to start when calculating TD bioavailaability for other SARMs. If anyone has a formula they use or know about, is willing to do some testing and share their results, or just knows more about this subject, please chime in.
Edit: answering question in the comments... why bother?
A liability of SARMs is suppression of HDL, otherwise known as good cholesterol. HDL reduces risk for heart disease. A good ELI5 is on WebMD. However, taking SARMs non-orally might help reduce or eliminate this undesirable trait, and perhaps others. For experienced users of SARMs, they will appreciate the importance of preserving HDL.
All in all, very exciting to try out, especially if we can show that this further reduces impact to the user as I believe it should.