Prince died of an accidental overdose of the powerful painkiller fentanyl, autopsy results released Thursday show.
The 57-year-old singer was found dead April 21 at his Minneapolis-area estate.
According to a one-page report released by the Midwest Medical Examiner's Office, Prince administered the drug himself, but the date he took it was unknown. The office said it has completed its death investigation and had no further comment.
Fentanyl is a synthetic opioid, 50 times more potent than heroin, that's partly responsible for a recent surge in overdose deaths in some parts of the country. It also has legitimate medical uses. More than 700 fentanyl-related overdose deaths were reported to the Drug Enforcement Administration in late 2013 and 2014.
The findings confirm suspicions that opioids played a role in the musician's death. After he died, authorities began reviewing whether an overdose was to blame and whether he had been prescribed drugs in the preceding weeks.
Prince's death came less than a week after his plane made an emergency stop in Moline, Illinois, for medical treatment as he was returning from an Atlanta concert.
The autopsy was conducted the day after Prince's body was found.
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.
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.
Prince's death from an opioid overdose is another example of the national opioid epidemic driven by prescription painkillers.
Prescription opioid overdoses reached nearly 19,000 in 2014, the highest number on record. Total opioid overdoses surpassed 29,000 that year when combined with heroin, which some abusers switch to after becoming hooked on painkillers.
What is a lethal dose?
It's tricky with opioids. Anyone who takes prescription opioid painkillers for a long time builds up a tolerance to the drugs. A dose that could kill one person might provide medicinal pain relief to another.
Experts in medical toxicology say it's important to know how much opioid medication a person has been using before a death to know how to interpret post-mortem blood levels. Pill bottles and medical history may become crucial evidence.
Does pain treatment lead to addiction?
Prince 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. Questions about Prince's health surfaced April 15, when his plane made an emergency stop in Moline, Illinois.
Becoming tolerant to opioid painkillers may lead some patients to seek stronger drugs from their doctors. Some users — whether they start as recreational users or legitimate pain patients — become addicted, experiencing an inability to control how much they take, so they use much more than is prescribed or seek out drugs on the black market.
With good management, however, opioids can offer relief to people with only a small risk of addiction, according to a 2010 review of the available studies.
Who is the medical examiner?
Dr. A. Quinn Strobl, who has been the chief medical examiner at the Midwest Medical Examiner's Office since late 2009, performed the autopsy on Prince herself. Her office is the official coroner for 19 counties in Minnesota, including Carver County, where he was found dead.
Strobl has been a practicing forensic pathologist since she finished her fellowship in 2005 and is board-certified in anatomic, clinical and forensic pathology.
According to a 2009 (Minneapolis) Star Tribune article, Strobl is a native of Philadelphia who attended Penn State and the University of Pittsburgh School of Medicine. She considered going into family practice and surgery, and decided being a medical examiner was a good mix of the two.
"I interact directly with the family. I deliver the diagnosis, and I answer a wide spectrum of questions," she told the newspaper. "I don't deliver the bad news. Hopefully, I deliver answers."