Fentanyl, the powerful painkiller that caused the death of pop star Prince, is a dangerous drug whose potential for addiction and abuse has led the Food and Drug Administration to enact strict guidelines over its prescription.
The Midwest Medical Examiner's Office in Minnesota, which released the musician's cause of death on Thursday, said Prince died of a self-administered accidental overdose of fentanyl. Authorities did not specify how the drug was administered.
While it remains unknown how Prince obtained the drug, experts say that there is an active illicit market for fentanyl and that the drug is often mixed with heroin or is passed off as heroin by dealers.
The results can be deadly for unsuspecting users.
"It's very potent. So the equivalent of a few grains of salt can be lethal in most people," said State University of New York at Buffalo professor Richard Blondell, whose research focuses on addictions.
He said that fentanyl is normally prescribed by doctors for the "severest of the severe" cases of pain, often for cancer patients or those who have undergone major surgery. Some estimates peg fentanyl as being as much as 100 times stronger than morphine. It was first introduced under the name Sublimaze in the 1960s, and was initially administered via an intravenous anesthetic.
Nowadays, patients can get a fentanyl dosage via tablets, patches, and injections -- or even lozenges referred to as "lollipops." The skin patch is known by the brand name Duragesic.
Experts say the drug is relatively easy to manufacture, which has led to a growing number of clandestine labs, including some in China, that pump out the substance.
"There's been a huge number of incidents when heroin has had fentanyl mixed into it and people overdose," said Dr. Matt Torrington, an addiction medicine research physician who has worked at the UCLA Integrated Substance Abuse Programs.
Some addicts rip open the patches in order to get a more direct hit, he said. "It's incredibly powerful in small doses," Torrington added.
The FDA has enacted strict guidelines in response to the drug's potential dangers.
Doctors have to go through special training and there are special agreements in which doctors and patients sign off saying they understand the risks involved.
The Drug Enforcement Administration said that it is seeing more cases of illegally sold fentanyl as well as fentanyl mixed with heroin. In a March 2015 nationwide alert, the DEA identified fentanyl as a public health threat after more than 700 fentanyl-related overdose deaths were reported between late 2013 and throughout 2014.
In 2014 alone, the National Forensic Laboratory Information System found there were 1,245 fentanyl drug seizures in Ohio alone; Minnesota was not among the top 10 states with the most seizures.
In many cases, the drug originates from China, with Mexican cartels buying the substance in bulk because it's cheaper than producing heroin or buying Colombian heroin wholesale.
A DEA spokesman said the administration is working on stemming the tide from China, but said that investigations can be difficult due to the numerous layers between Chinese companies and the ultimate U.S. destinations.
The Carver County Sheriff's Office, which previously said it was investigating the circumstances surrounding the pop star's death, had no further comment on Thursday about his cause of death.
"We are 5% of the world's population and yet we consume 80% of the opioids on the planet," said Dr. Drew Pinsky, an addiction specialist and television personality. "The over-prescribing is out of control, and finally, this is just getting people's attention."
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