The American Addiction Centers laboratory tested more than 10,000 urine samples in 2018.

Of the tests that were positive for heroin, 40% also contained fentanyl.

Of cocaine-positive tests, 28% also contained fentanyl.

A Nashville-area laboratory that analyzes drug tests from across the country says last year it found fentanyl in about 40 percent of all urine samples that contained heroin and 28 percent of samples that contained cocaine, providing more evidence of how deeply America's deadliest opioid has infiltrated the nation’s illegal drug supply.

These statistics come from more than 10,000 drug tests at the American Addiction Centers lab in Brentwood, which analyzes urine samples from 20 treatment centers run by the company in nine states. Clients are drug tested as they enter rehab and throughout their treatment programs.

Collectively, those tests offer a unique measure of the troubling spread of fentanyl through the American drug market, where addictive drugs that were already dangerous have become far deadlier. Fentanyl is about 50 times stronger than heroin, and a lethal dose is no bigger than two grains of sand.

“I think the take home message is that users do not know what they are buying,” said Dr. Howard Taylor, lab director for American Addiction Centers, which released the findings this week. “They have no idea what is in the heroin or cocaine they are buying.”

Fentanyl became the deadliest drug in Nashville in 2017 and was linked to 500 fatal overdoses in Tennessee that same year. Nationwide, fentanyl and other synthetic opioids were responsible for nearly 30,000 deaths in 2017.

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Despite this lethality, fentanyl can be easily and cheaply purchased online and is often smuggled into the United States through mail sent from China. Drug dealers then mix fentanyl into low-grade heroin or cocaine to boost potency and maximize profits, creating street drugs that can cause overdoses, even for hardened addicts who have developed strong tolerances to regular heroin or cocaine.

Although the American Addiction Centers statistics are alarming, they come with one major caveat: Laboratory tests confirm only that fentanyl was found alongside heroin or cocaine in a person’s urine, but do not necessarily verify that the drugs were cut with fentanyl. In some cases, a test subject may have used heroin and fentanyl separately, but Taylor said it is most likely that the vast majority of these cases involve heroin and cocaine that are tainted with fentanyl.

“It makes sense from a drug dealer’s perspective, because the profit level for fentanyl is huge,” Taylor said. “One kilogram of pure fentanyl can yield a drug dealer a profit of over $1 million."

Fentanyl-laced drugs cause slew of overdoses

The lab results also align with what law enforcement is seeing on the ground level in Tennessee, where fentanyl is often found cut into heroin, cocaine, meth and counterfeit pills, said T.J. Jordan, assistant director of the Tennessee Bureau of Investigation’s drug division.

As an example, Jordan pointed to Clarksville, where only a few days ago police put out a public warning saying that drugs laced with fentanyl had caused a slew of overdoses.

“We have been sounding the alarm and beating the drum so much trying to warn people that what they are buying may not be what it appears,” Jordan said. “What you take today may simply kill you tomorrow. And no one is heeding that warning.”

American Addiction Centers recorded similar results last year. In 2017, the lab found fentanyl in 43 percent of urine samples that tested positive for heroin and 27 percent of samples that tested positive for cocaine.

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Brett Kelman is the health care reporter for The Tennessean. He can be reached at 615-259-8287 or at brett.kelman@tennessean.com.