A topical lotion infused with cannabis is on display at the Perennial Holistic Wellness Center dispensary on July 25, 2012 in Los Angeles, California. (David McNew, Getty Images)

If I use cannabis topicals, will I test positive on a THC drug test?

Hey, Cannabist!
I was wondering: Will marijuana topicals show up in a drug test, because I’ve been looking everywhere but I don’t seem to get a clear answer for it. I have been using it for about two weeks now and I’m already going my fourth week without smoking so I just want to know if it will show in my upcoming drug test?
–Topical Tony

Hey, Tony!
It looks like this is a two-part question. A) Could marijuana topicals cause a positive drug test? and B) Will you pass an upcoming drug test?

First things first. For those unfamiliar, topicals refer to a wide range of cannabis-infused products. They come in an array of forms — lotions, salves, balms, ointments and sprays — and are applied to the skin to provide a localized effect. Topical use is typically not intoxicating, and rather is considered therapeutic, such as massages with cannabis lotions.

Is there a risk of THC absorbing through the skin and causing a positive result in a marijuana drug test?

“Most likely the answer is no,” said Paul Armentano of the National Organization for the Reform of Marijuana Laws.

“THC is lipid soluble so one would expect very little THC to enter the bloodstream via transdermal delivery,” Armentano told The Cannabist via email. He is deputy director of NORML and recipient of the Alfred R. Lindesmith Award for Achievement in the Field of Scholarship and author of numerous articles on drug testing.

To get more information on topicals and the bloodstream, I reached out to Dahlia Mertens, CEO of Mary Jane’s Medicinals, a Colorado company making topicals in Telluride since 2010.

“The cannabinoids in topicals do not actually enter the bloodstream (that is why topicals do not get you high), instead they interact with the peripheral nervous system,” Mertens said in an email. “As a result, people that use our topicals have not tested positive for THC in drug tests.”

So, in Merten’s business experience, none of her customers have tested positive in a drug test from her topical products.

However, the makers of some topical products, like the transdermal THC patches from Colorado-based Mary’s Medicinals assert the product is delivered directly to the bloodstream.

Could the transdermal THC patches cause a positive drug test? To get more information, I contacted analytical chemist Noel Palmer, former chief scientist at Mary’s Medicinals. He is currently chief scientist at Colorado extracts company Evolab and recipient of the 2014 Americans For Safe Access 2014 Researcher of the Year award. (Disclosure: I also worked for Mary’s Medicinals in 2015, but am no longer affiliated with the company.)

Palmer says via email: “THC alone and by itself will not permeate through the skin into the bloodstream, just as most drugs won’t. The skin is designed to keep things out, and it does a really good job at doing this.”

OK, if THC isn’t absorbed into the skin, how can the patches be effective?

In terms of successful transdermal delivery, Palmer says: “We are not re-inventing the wheel, we are using past precedent to make it happen with cannabis.”  

He cites examples of fentanyl, nicotine, hormones and steroids as compounds that will not be absorbed and transferred to your bloodstream if you put them directly on your skin. They have been specially formulated for transdermal delivery through patches and creams. Palmer adds, “Fentanyl patches are well accepted by the FDA, which proves that there’s efficacy. The FDA wouldn’t allow them to be made and sold otherwise.”

How are these transdermal formulations designed for absorption? In brief, Palmer indicates if the outer skin layer is penetrated by a carrier substance in the patch, then the Active Pharmaceutical Ingredient (API) can be circulated into the bloodstream.

He says, “The common theory is that if you disrupt the stratum corneum with ‘permeation enhancers’ and/or ‘carriers’ – then you can promote diffusion of API into the bloodstream, even if it’s lipophilic. This has been proven time and time again with other drugs, which is where the precedent came from. THC isn’t that different. Permeation enhancers can be liposomes, fatty acids, terpenes, etc.” 

That makes sense, the skin is permeated by a substance that enables the transfer of the active ingredient into the bloodstream.

Based on Palmer’s explanation about how transdermal patches work, it stands to reason that when THC is delivered to the bloodstream and processed by the body, it would register on a marijuana drug test, and Palmer verified that it “would likely generate a positive result when testing for THC and THC metabolites,” depending on when the patch was used and when the drug test was administered.

Good to know. But will you  pass your upcoming drug test since you ceased smoking for four weeks?

As discussed in a previous Ask The Cannabist column, physician and marijuana researcher Dr. Alan Shackelford noted there are many factors involved in how quickly THC is processed by the body and in short, it could take as long as three months to test clean of THC.

While it’s believed the use of certain cannabis topicals won’t lead to a positive drug test, no definitive research has been done on consumers who only use infused topicals.

If you expect to take a drug test for work, court or another reason, it may be better to communicate before the test and ask permission than try to explain a potentially positive analysis after the results come back. Ultimately, you’re responsible for what you put in — or on — your body. XO

Ask The Cannabist: Clearly you have questions about marijuana, be it a legal concern, a health curiosity or something more far-reaching. Email your queries to askthecannabist@gmail.com.