Prince died of an overdose of the powerful opioid fentanyl, according to autopsy results released in June. Among the questions investigators were reviewing was whether Prince had a prescription for painkillers before his death.

A person close to the investigation of Prince’s death told The Associated Press on Sunday that pills found in Prince’s home marked as acetaminophen-hydrocodone actually contained fentanyl, suggesting they were counterfeit pills obtained illegally. The person spoke on condition of anonymity because the investigation was ongoing.

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.

Some information on fentanyl:

 

What is fentanyl?

Fentanyl is a synthetic opioid, 50 times more potent than heroin, that’s responsible for a recent surge in overdose deaths in some parts of the country. It also has legitimate medical uses.

Doctors prescribe fentanyl for cancer patients with tolerance to other narcotics. It comes in skin patches, lozenges, nasal spray and tablets. Because of the risk of abuse, overdose and addiction, the Food and Drug Administration imposes tight restrictions on fentanyl; it is classified as a Schedule II controlled substance.

Some pharmaceutical fentanyl is illegally diverted to the black market. But most fentanyl used illicitly is manufactured in clandestine labs. The U.S. Drug Enforcement Administration has tied fentanyl seizures to Mexican drug-trafficking groups. On the street, fentanyl is sold alone as powder, added to heroin or made into counterfeit OxyContin pills. Users don’t always know when they’re taking fentanyl, increasing the risk of fatal overdose.

The DEA issued a nationwide alert about fentanyl overdose in March 2015. More than 700 fentanyl-related overdose deaths were reported to the DEA in late 2013 and 2014. Since many coroners and state crime labs don’t routinely test for fentanyl, the actual number of overdoses is probably much higher.

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.

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.