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Delta-8-THC: A new synthetic cannabinoid poses problems for testing

In states where recreational cannabis products are still illegal, authorities are seeing a large increase in sales of products containing delta-8-THC. “Delta-8” is a chemical cousin of delta-9-THC, the main cannabinoid responsible for the euphoria of marijuana. Delta-8 is less potent than delta-9, but interacts with the same brain receptors and can produce a “high.” Unfortunately, delta-8 interferes with testing for delta-9 in both presumptive and definitive urine drug tests, according to Quest Diagnostics Medical Science Liaison, Jack Kain, PharmD.

The rise in the sale of delta-8 products is tied to the 2018 federal Farm Bill, which made it legal to grow hemp. Like marijuana, hemp is a variety of the plant Cannabis sativa, but is bred to contain less than 0.3% delta-9, too little for the “high” of marijuana. Hemp does contain large amounts of cannabidiol (CBD), which is mostly legal and widely used for its purported health benefits.

CBD can be chemically converted into delta-8, Dr Kain said, “and in recent years, it has grown in production and selling as medicinal or recreational cannabis products, resulting in the proliferation of delta-8-THC vape liquids, tinctures, and edibles.”

The legality of delta-8 is in something of a gray zone. According to the most recent rule from the Drug Enforcement Administration, “All synthetically derived tetrahydrocannabinols remain schedule I controlled substances,”but the rule did not clarify whether such compounds converted from CBD, a legal hemp product, are included. Absent such clarification, many states that have not legalized recreational marijuana have declared delta-8 to be illegal.

The similarity in the names of delta-8-THC and delta-9-THC is an indication of how close they are structurally, differing only in the position of one double bond in one ring within the THC molecule. That similarity carries over into their major urinary metabolites, delta-8-THCA and delta-9-THCA, which also differ in only one bond.

Those similarities can lead to challenges in testing, Dr Kain said. For presumptive testing, which uses an immunoassay, the structural similarity between the two metabolites leads to high antibody cross-reactivity. Thus, a presumptive test for a person who has used a delta-8 product (which may be legal in the state where he or she resides) may give a false-positive for delta-9-THC. The two metabolites also have the same molecular weight and very similar chemical properties, meaning delta-8-THCA can interfere with detection of delta-9-THCA, leading to a false-negative on definitive testing.

Clinicians should keep these important caveats in mind when using the results of a test for delta-9-THC in counseling their patients.

Published date: July 12, 2021


1 Federal Register, August 21, 2020. “Implementation of the Agriculture Improvement Act of 2018.”

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