Updated: 2:10 p.m. | Posted: 11:10 a.m.
Prince's autopsy results show the music superstar died of "fentanyl toxicity" and that the drug was self-administered. His death was ruled an accident.
The findings released Thursday confirm suspicions that opioids played a role in the musician's death, although the autopsy results don't say whether the fentanyl that killed Prince was prescribed to him by a doctor.
Fentanyl is one of the most dangerous opioid painkillers, Dr. Charles Reznikoff, an addiction medicine specialist at Hennepin County Medical Center, said Thursday.
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"Fentanyl is what I call the Ebola of opioids," he added. "Fentanyl kills you quickly, very quickly, as opposed to many of the other opioids that take a long time and are less apt to kill you" during an overdose.
"Fentanyl is so potent, that any little error with the use of fentanyl leads to death," he added.
The National Institute on Drug Abuse describes the drug as a "powerful synthetic opiate analgesic similar to but more potent than morphine."
• Related: Here's why Minnesota has a big problem with opioid overdoses
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It's available in several forms, including as a lozenge and in IVs for patients in surgery.
It can also be administered in a skin patch designed to release the drug into the body over a longer period of time, Reznikoff said. The U.S. Food and Drug Administration has warned repeatedly about the dangers of fentanyl patches.
Law enforcement officials in the region have recently warned about fentanyl overdoses, although officials traced that fentanyl supply to an illegal lab in Mexico.
The 57-year-old singer was found dead April 21 at his Minneapolis-area estate. The Carver County Sheriff's Office continues to investigate.
According to the autopsy report, Prince was 112 lbs. and 5 feet 3 inches tall at the time of his death. He had a scar on his left hip and a scar on his right lower leg. He was wearing mostly all black: a black cap, black shirt, black pants and black socks.
The star's death came less than a week after his plane made an emergency stop in Moline, Ill., for medical treatment as he was returning from an Atlanta concert.
The Associated Press and other media reported, based on anonymous sources, that Prince was found unconscious on the plane, and first responders gave him a shot of Narcan, an antidote used in suspected opioid overdoses.
At least two doctors' names have come up in the death investigation being conducted by the Carver County Sheriff's Office, the U.S. Attorney's Office in Minnesota and the Drug Enforcement Administration.
Dr. Michael Todd Schulenberg, a family practitioner, treated Prince twice in the weeks before his death and told investigators he prescribed medications for the singer. The medications were not specified in a search warrant for the Minnesota hospital that employed Schulenberg at the time.
Schulenberg saw Prince April 7 and April 20 — the day before his death — according to the warrant. Schulenberg's attorney has declined to comment on the case.
Dr. Howard Kornfeld, a California addiction specialist, was asked by Prince's representatives on April 20 to help the singer.
Kornfeld sent his son Andrew on a redeye flight that night, and Andrew was among the people who found Prince's unresponsive body the next morning, according to Kornfeld's attorney, William Mauzy.
The younger Kornfeld, who is not a doctor, was carrying buprenorphine, a medication that can be used to treat opioid addiction by easing cravings and withdrawal symptoms, Mauzy said, explaining that Andrew Kornfeld intended to give the medication to a Minnesota doctor who had cleared his schedule to see Prince on April 21.
Mauzy has refused to identify that doctor. Schulenberg is not authorized to prescribe buprenorphine.
• Podcast: Prince Remembered
Prince's death came two weeks after he canceled concerts in Atlanta, saying he wasn't feeling well. He played a pair of makeup shows April 14 in that city, and then came the emergency landing in Moline. He was scheduled to perform two shows in St. Louis but canceled them shortly before his death.
The superstar had a reputation for clean living, and some friends said they never saw any sign of drug use. But longtime friend and collaborator Sheila E. has told the AP that Prince had physical issues from performing, citing hip and knee problems that she said came from years of jumping off risers and stage speakers in heels.