Breath Test May Detect Marijuana Use

Deborah Brauser

December 04, 2013

A new breath test may help in screening drivers or even employees for recent marijuana use, preliminary research suggests.

A small pilot study of 25 adult long-term or occasional smokers used a new test that detects the presence of delta-9-tetrahydrocannabinol (THC), the main psychoactive chemical in marijuana, in the breath of those who used the substance within 30 minutes to 2.5 hours prior.

"The whole issue of drugged driving is key right now," senior author Marilyn A. Huestis, PhD, chief of chemistry and drug metabolism at the Intramural Research Program at the National Institute on Drug Abuse (NIDA) and adjunct professor at the University of Maryland in Baltimore, told Medscape Medical News.

"In fact, the Office of National Control Policy has made the reduction of drugged driving 1 of their top 3 initiatives for the last several years. It's a really big health and safety problem," she said.

However, she noted that when it comes to the study's findings, more work needs to be done.

"This is very interesting and exciting, but we have a lot of science to develop before this type of test can end up by the roadside. We need to find out about how drugs get into breath, how long they're in there, and then we have to develop the methods that could then be used in the field," said Dr. Huestis.

"It's a ways off, but it's a big step forward," she added.

The study was published online in Clinical Chemistry.

More Teens Driving High

A recent study published in the American Journal of Public Health and reported by Medscape Medical News showed that more teens are now driving while high, and another study showed that drivers who consumed cannabis within 3 hours of driving were twice as likely to cause a serious road accident as those who did not use the substance.

However, in an editorial that accompanied the latter study, Wayne Hall, PhD, from the University of Queensland in Australia, noted that public health education about these dangers are probably not enough to deter cannabis users from driving.

"They will also need to be persuaded that they are at risk of their cannabis use being detected," he wrote.

Dr. Marilyn Huestis

Dr. Huestis reported that although roadside saliva testing has been used in Europe and Australia and has been approved in several states in the United States, THC can be detected for up to 48 hours in oral fluid. This means its detection may not coincide with impairment.

On the other hand, she noted that noninvasive breath alcohol tests are widely used by law enforcement. "Everyone would love it if we could have a breath test like we have for alcohol," she said.

In the current study, the investigators enrolled 13 long-term marijuana smokers (partaking more than 4 times per week, on average) and 11 occasional smokers (partaking fewer than 2 times per week).

Exhaled breath was collected from all participants (between the ages of 19 and 41 years) to measure THC; 11-nor-9-carboxy-THC (THCCOOH), a metabolized version of THC; and cannabinol before and after controlled smoking of a single 6.8% THC cigarette.

Measurements were taken at several intervals up to 21 hours after the controlled smoking episode.

"Sample analysis included methanol extraction from breath pads, solid-phase extraction, and liquid chromatography–tandem mass spectrometry quantification," report the researchers.

THC Detected

Results showed that none of the participants' breath samples contained THCCOOH, and only 1 participant had a breath sample containing cannabinol.

However, all of the breath samples from the long-term smokers contained THC at the 0.89-hour mark. In addition, 77% of the long-term smokers' samples still contained THC at the 1.38-hour mark, and 54% contained THC at the 2.38-hour mark.

Interestingly, only 1 long-term smoker still showed positive THC findings at the 4.2-hour mark.

The collection times were a little different for the occasional smokers. Still, 91% of their breath samples were positive for THC at the 0.95-hour mark. This number dropped to 64% at the 1.49- hour mark. Only 1 of these smokers had no detectable THC at any measuring point.

The breath sample collection devices also contained polymeric filter pads, which were enclosed in plastic chambers.

Direct analyte recovery from the breath pads was 83% to 86% for THC, 84% to 91% for cannabinol, and 85% to 97% for THCCOOH.

Cannabinoids on the breath pads showed a concentration change of less than 18.2% (defined as "stable") for 8 hours at room temperature and for 6 months at -20 degrees Celsius.

The median THC breath concentration was 94.9 pg per pad in the long-term smokers and 61 pg per pad in the occasional smokers.

Both of the smoking groups showed significantly decreased THC breath concentrations over time (P < .0001).

Short Window

Overall, "breath may offer an alternative matrix for testing for recent driving under the influence of cannabis, but is limited to a short detection window," the researchers summarize.

However, they note that the driving impairment window extends past the .5- to 2-hour breath detection window.

"I think oral testing is ready for prime time now, and that's a good thing. With breath testing, we're just starting," said Dr. Huestis.

"I think the concern is whether or not there will be high enough concentrations in breath that it's realistic to use for the workplace, for accident investigation, etc ― especially because our window of detection is so short."

She reported that NIDA investigators are planning to conduct further studies into these issues and are currently assessing whether cocaine use can be detected with breath tests.

"A breath test is clearly a distance away, but I think it could be a good tool. For now, oral testing is available and ready. And it would go a long way towards identifying problematic drugged driving," said Dr. Huestis.

The study was funded by NIDA's Intramural Research Program. Dr. Huestis and 4 of the other 5 study authors have disclosed no relevant financial relationships. The other study author reports part ownership in SensAbues, which produces the sample collection device used.

Clin Chem. Published online September 17, 2013. Abstract

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