Alprazolam—sold under the brand name Xanax—was involved in more than 6,000 drug overdose deaths in 2016.

An anti-anxiety medication is among the deadliest drugs in America.

Alprazolam, which you’re probably more familiar with under the brand name Xanax, was involved in more than 6,000 drug overdose deaths in 2016, according to a new report from the CDC’s National Center for Health Statistics (NCHS). The data, published this week, tallied the drugs most frequently involved in such deaths from 2011 to 2016 as reported on death certificates.

Over that time period, drug overdose deaths increased 54%, from 41,340 in 2011 to 63,632 in 2016, according to the report. Other CDC data shows that drug overdose deaths have only continued to increase; more than 70,000 Americans died of a drug overdose in 2017, and overdose deaths are thought to be contributing to our decreasing lifespans.

Most of the 18,335 overdose deaths in 2016 were linked to fentanyl, the synthetic opioid that’s 50 times stronger than heroin and 100 times stronger than morphine. From 2012 to 2015, heroin had been the deadliest drug, and it was tied to 15,961 overdose deaths in 2016.

Cocaine (11,316) and methamphetamine (6,792) were the next deadliest drugs in 2016, followed by the totally legal (although not without risks) prescription anti-anxiety medication alprazolam. It’s used to treat anxiety disorders and panic disorder by decreasing arousal in the brain, but it was involved in 6,209 overdoses in 2016. It was also involved in 468 overdose deaths that were deemed to be suicides, making it the fourth deadliest drug used for suicide in the report.

Alprazolam is in a class of medications called benzodiazepines, and it’s not the only one tied to overdoses. Diazepam (Valium)—also used to treat anxiety—was linked to more than 2,000 overdose deaths in the new report. In 96% of drug overdoses that involved either of these benzodiazepines, other drugs were also involved. “For deaths in which multiple drugs are involved, whether the death was caused by just one of the drugs present or was caused by a combination of some or all of the drugs present cannot be determined from the literal text analysis,” the report authors wrote.

Experts have previously raised concerns about ever-increasing rates of benzodiazepine prescriptions—as well as the fact that the meds are known to be deadly when taken in combination with opioids. The FDA puts Boxed Warnings, the strongest warnings possible, on opioids and benzodiazepines that list the dangers of using the two together. These can include slowed breathing and death.

From 1996 to 2013, benzodiazepine prescriptions increased by 67%, and over roughly the same time span, benzodiazepine-related overdose deaths rose from 1,135 to 8,791, according to a New England Journal of Medicine report from February 2018.

“Despite this trend, the adverse effects of benzodiazepine overuse, misuse, and addiction continue to go largely unnoticed,” cautioned the authors, from the Department of Psychiatry and Behavioral Sciences at Stanford University. “Three quarters of deaths involving benzodiazepines also involve an opioid, which may explain why, in the context of a widely recognized opioid problem, the harms associated with benzodiazepines have been overlooked.”

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