An assortment of edible marijuana products. Most edibles in a recent study inaccurately described the amount of THC on their labels.

By CATHERINE SAINT LOUIS

An analysis of 75 edible marijuana products sold to patients in Seattle, San Francisco and Los Angeles found that labels on just 17 percent accurately described their levels of THC, the main psychoactive ingredient, researchers reported Tuesday.

Sixty percent of the products had less THC than their packages advertised, and 23 percent of them had more THC than claimed.

“We need a more accurate picture of what’s being offered to patients,” said Dr. Donald Abrams, the chief of hematology and oncology at San Francisco General Hospital. He was not involved in the new study, which was published in JAMA.

“What we have now in this country is an unregulated medical marijuana industry, due to conflicts between state and federal laws,” Dr. Abrams said.

After ingesting marijuana, patients experience the maximal high one to three hours later. (It is felt within minutes after smoking.) Inaccurate labels complicate the consumption of marijuana for medical purposes.

Products with too little THC, or tetrahydrocannabinol, may fail to deliver symptom relief to those with debilitating conditions like chronic pain, and those with too much may overwhelm users.

Some of Dr. Abrams’s older cancer patients have tried edibles, he said, because they do not want to smoke marijuana. But some have eaten too much THC, with unpleasant results such as severe anxiety.

In the new study, cannabis candy, drinks and baked goods from 47 brands were tested by the Werc Shop, a laboratory with outposts in California and Washington State.

The Johns Hopkins University School of Medicine paid for the study except for the cost of the testing, which was covered by the Werc Shop. The company’s chief executive, Jeffrey Raber, is a study author.

Some discrepancies were notably large: In one case, a product had just three milligrams of THC even though its label claimed 108, said Ryan Vandrey, the study’s lead author and an associate professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine.

The researchers declined to name specific manufacturers or products. “I didn’t want to get sued,” Dr. Vandrey said.

“The point is not to say, ‘Hey, X medical marijuana company, you’re bad,’ ” he added. The more serious issue is that “we don’t have the kind of quality assurance for edibles that we have for any other medicine.”

The analysis found some geographical differences: The likelihood of having edible medical marijuana with more THC than advertised was higher in Los Angeles, while the likelihood of having it with less THC than labeled was greater in Seattle.

The researchers also tested each product for cannabidiol, or CBD, a nonpsychoactive ingredient of marijuana that is being studied in purified form as a possible aid to children with intractable epilepsy.

Forty-four products had detectable levels of CBD, though only 13 disclosed CBD. Nine had less CBD than labeled; four had more.

One limitation was that just one laboratory performed the analysis, medical and lab experts cautioned. Methodologies and results vary from lab to lab.

Some variability in test results is routine in this sort of analysis, so the researchers classified labels as accurate if the THC content was within 10 percent of the claimed levels.

Still, Remy Kachadourian, a chemist who has analyzed edible marijuana, suggested that 10 percent variability was too narrow.

“Plus or minus 15 percent is acceptable, and not only in my lab, but other labs in Colorado,” said Dr. Kachadourian, a senior scientist at CMT Laboratories in Denver.

Even though 23 states and the District of Columbia have medical marijuana programs, the federal government does not recognize marijuana as medicine and considers it illegal.

“When that changes,” Dr. Abrams said, “we’ll see the industry rushing to standardize dosing, as well as laboratory testing of products.”

http://mobile.nytimes.com/2015/06/24/health/labels-for-edible-marijuana-often-err-on-potency-study-says.html?ref=health&_r=1&referrer=

Thanks to Mike Moore for bringing this to the attention of the It’s Interesting community.

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