Drug Testing for Marijuana: How to Address Challenges with THC Toxicology

Today’s marijuana is a different animal than the marijuana we knew 30 years ago. Higher THC content (from under 4% in 1995 to more than 15% in 2021) has changed the effects commonly connected to cannabis use, often with dangerous consequences.

But that increased concentration of THC has come alongside two key challenges: the perception of marijuana in the public and the difficulty marijuana toxicology presents when determining impairment and use patterns.

Drug testing for marijuana has historically been challenging. But today’s increased prevalence and potency make it even more important to find a solution, both for immediate needs and for continuing safety.

Why Drug Testing for Marijuana is an Urgent Issue

Many states in the US have legalized or decriminalized marijuana use in recent years, whether for recreational or medical purposes. That cultural shift is evident in public opinion polls, which changed dramatically at the turn of the millennium. What was once considered a dangerous and harmful drug is now considered relatively safe, according to a 2019 Pew Research Center report. 50 years ago, only 19% of the US population believed marijuana should be legalized. Today, over 67% of the population supports legalization.

More Widely Accepted, More Widely Used

Marijuana use is more ubiquitous than ever before, according to both NIDA reports and an April 2022 YouGov survey. On page 8 of the report, the survey states that 44% of the respondents had used marijuana within the past year.

Jen Rankin, one of our PharmChek® sales representatives, is not surprised by that number. She says that recent legalization in Missouri, where she lives, has had a strong impact on her community.

“Being in a state where it's been newly legalized, I smell it when I walk in public places. That's a new experience. It seems like people see it as the new fun thing, even people that probably never considered it before.”

And public perception is different as well. What was once considered a powerful and dangerous gateway drug is now thought to be mostly benign.

“I’m surprised by the people that are trying it now, people I never thought would try marijuana.”

Sales rep Richard Combs has seen the change in public perception as well.

“In elementary school, I remember police officers talking about marijuana the same way they talked about cocaine and heroin. Now, with marijuana legalized in places like California, you see celebrities smoking it in public, and you see more people on TV using it. It just creates this image that it's not that bad.”

More Potent Than Before

But that shift parallels another trend in cannabis: increased potency. PharmChek® Chief Revenue Officer Kerri Wagner has heard about this increase from caseworkers and law enforcement agents that see it firsthand:

“What I've been hearing when I talk to our customers is that the pot from the 80s and 90s is way different from what they are dealing with now in terms of strength.”

And there are potentially dangerous consequences to these shifts.

In the past, marijuana was associated with effects like elevated mood, loss of social inhibition, increased appetite, and pupil dilation. These psychoactive effects were relatively mild, with an average of only 10mg of THC in a single joint.

But today, when a single joint can hold as much as 15 times the THC (anywhere from 60 to 150mg in many confiscated samples), cannabis consumption can result in much more serious effects, including vomiting, hypertension, time-space distortions, hallucinations, ataxia, and seizures. There are even reports of cardiac arrhythmia and stroke in some cases.

The result is that drug testing for marijuana becomes a pressing safety measure for both individuals and the communities in which they live—providing safety measures and detection methods for impairment and limiting overdose risks. But marijuana toxicology comes with challenges because of its complex chemical profile.

The Challenge of Marijuana Toxicology Testing

While the dangers associated with cannabis use have increased, drug testing for marijuana still has challenges that limit its accuracy and reliability in many cases. And cannabis’s complex metabolization process is largely to blame.

The psychoactive chemical in marijuana is delta-9-THC (called THC or Delta-9 in short form). This fat-soluble chemical quickly enters the bloodstream when inhaled, taking effect in just a few minutes (edibles usually take an hour or more). From there, THC is either metabolized in the liver and expelled through the kidneys, or it gets stored in fatty tissues, where it will slowly release for up to 10 days (for chronic users, this process could persist for 30 days or more). The challenge, then, is finding reliable ways to interpret test results that could be inconsistent with recent use patterns. And that challenge has been present for decades.

Doug Crook, PharmChem’s toxicology expert, knows the struggle well.

“Long before the Sweat Patch, marijuana had always been our Achille’s heel. It provides the biggest challenge of the drugs that we’re looking for.”

Metabolite Detection Won’t Tell the Full Story

Most drug testing for marijuana focuses on THC’s metabolites (carboxy-THC and 11-hydroxy-THC). But metabolite detection alone is an incomplete picture of recent use, specifically with testing methods like urinalysis.

Hydration levels can dramatically change results in drug screenings. That variable makes it difficult to accurately determine recent use from residual use, one of the most prevalent objections to positive test results, as well as creating the opportunity for false negatives.

According to Crook, it has historically taken considerable effort to account for hydration levels.

“When urine was the only option for THC, back before the PharmChek® Sweat Patch, we had to watch creatinine levels for every sample.”

Since hydration directly affects THC metabolite concentrations in testing, a creatinine-normalized metabolite ratio is required to better understand many results.

“With urine testing, you need to know if a sample is concentrated or diluted,” says Crook. “Your creatinine levels are the key, but you need to calculate the ratios. You can’t just go by raw numbers. And that was always a pain to get right.”

In addition, past cannabis use can cause false positive drug screen results for as many as 30 days after the last use in chronic users. THC is stored in fatty tissues in the body and then slowly released for metabolization. Those residual metabolites can then show up on screenings and create confusion for case managers, courts, and recovery counselors.

Delta-9 Detection is Better, but Test Methods Make a Difference

Testing for active Delta-9 is more reliable than testing for metabolites, but it comes with strict time constraints for snapshot testing methods like blood and saliva. Blood samples only provide an accurate picture for around 24 hours, and saliva has about the same time limit.

But in both cases, the accuracy of the results can be compromised by things like health conditions, eating or drinking prior to sample collection, and, again, hydration levels.

Alternatively, PharmChek® is not affected by eating, drinking, or hydration levels, and can begin detecting recent use up to 24 hours after the last use of marijuana. This gives the PharmChek® Sweat Patch an advantage over other testing methods, specifically in recovery efforts.

Impairment Testing Isn’t Dependable Yet

However, field sobriety testing for marijuana impairment is still unreliable, even in motor skill and coordination testing. Breathalyzers have also proven undependable, as THC spends little time in the bloodstream, unlike alcohol. The most reliable screening method is oral swabbing on site as a presumptive positive. Even then, THC levels don’t predictably correlate to impairment levels.

More Confident Results for Marijuana Drug Testing

The presence of THC metabolites is not a clear indication of recent use. And with the narrow collection windows for many testing methods, cannabis testing takes more effort to achieve accuracy. Not only is it critical to confirm the parent drug instead of metabolites, but it’s also critical to confirm screening results with more advanced lab testing methods.

Enzyme immunoassay screening (EIA) has improved over the last decade, but it still produces false positives and false negatives for marijuana use. Today, the most reliable confirmation method is liquid chromatography-tandem-mass spectrometry (LC-MS/MS). This testing method can detect the molecular signature of active THC rather than just the residual evidence of past use. If a test result returns positive after LC-MS/MS confirmation, there is no doubt that a donor has used marijuana.

This confirmation system eliminates the doubt of a substance’s presence in a sample, but the sample could still be adulterated in many collection methods. This challenge is where the PharmChek® Drugs of Abuse Sweat Patch demonstrates its unique advantage over other testing methods.

The PharmChek® Difference

The PharmChek® Sweat Patch is designed to provide the most accurate, effective, and simple drug testing process available for test-forward needs. For more than 30 years, we’ve been a trusted and court-supported drug testing method for drug courts, probation and parole departments, and recovery programs in the U.S. and abroad.

We’ve earned this trust through our commitment to industry-leading methodologies and agency-focused design and support. No other testing solution on the market today can offer the same benefits.

Why EIA and LC-MS/MS Together?

When an EIA screening and LC-MS/MS confirmation are used together, the results of drug testing for marijuana become much more reliable than a simple EIA. The PharmChek® Drugs of Abuse Sweat Patch solves many of the problems that make other tests less reliable.

Read about our court-supported results to see the reliability of the PharmChek® Sweat Patch in real-world cases.

Why Insensible Sweat?

Urinalysis and saliva testing have benefits, but insensible sweat eliminates many of the challenges that come with those tests. Both urine and swab tests can be adulterated through eating or drinking before the test. Insensible sweat, however, isn’t affected by these factors. In fact, this sample collection method is nearly impossible to adulterate undetected.

Learn how our design keeps samples safe and reliable.

Why Test Forward?

All other tests look at past use. Only PharmChek® offers insights into sobriety, use patterns, and compliance through its collection process. With urine, blood, saliva, and hair tests, agencies and programs can only see what has happened in the past. PharmChek® keeps wearers of the sweat patch accountable for their future choices.

Learn how the PharmChek® Drugs of Abuse Patch helped one drug court client find freedom from addiction here.

Why the PharmChek® Patch?

With 25 years of court-supported results, a tamper-evident design, and sample collection that aids in recovery instead of just punishment, the PharmChek® Sweat Patch is the obvious choice for agencies and programs that need to support sobriety efforts through consistent accountability.

Instead of fighting against false positives, battling adulteration attempts, and dealing with detection gaps in sample collection, the PharmChek® Patch allows court officials and case managers to equip individuals with the tools they need to remain accountable every day, all day long, for up to 10 days without hassle. Start testing forward today and see the difference PharmChek® makes in your recovery support efforts.