The investigation into the death of “Friends” star Matthew Perry has led to a sweeping indictment that pulled in five people who prosecutors say contributed to his ketamine overdose in October, including two doctors and a street dealer involved in providing Perry large amounts of the powerful anesthetic.

Here’s what to know about ketamine.

What is Ketamine?

Ketamine is a powerful anesthetic approved by U.S. health regulators for use during surgery. It can be given as an intramuscular injection or by IV.

The drug is a chemical cousin of the recreational drug PCP. Ketamine itself has been used recreationally for its euphoric effects. It can cause hallucinations and can impact breathing and the heart.

Matthew Perry’s Ketamine Use

Ketamine has seen a huge surge in use in recent years as a treatment for depression, anxiety, and pain. While the drug isn’t approved for those conditions, doctors are free to prescribe drugs for so-called off-label uses.

In Perry’s case, he was using it to treat depression. He was receiving ketamine infusion therapy from his physicians, but prosecutors said the actor turned to other sources when his doctors refused to give him more doses.

Prosecutors revealed that Perry obtained ketamine illicitly through a network that included a pair of doctors, his assistant, and a woman they dubbed the “Ketamine Queen.” Perry’s assistant, who has pleaded guilty to one count of conspiracy to distribute ketamine causing death, injected the actor with ketamine—several times on the day he died.

“We are not talking about legitimate ketamine treatment,” U.S. Attorney Martin Estrada said while announcing the charges. “We’re talking about two doctors who abused the trust they had, abused their licenses to put another person’s life at risk.”

Other Uses of Ketamine

Ketamine has also been used by paramedics as a sedative, often while working alongside police when they believed subjects were out of control. Some states and agencies have begun to rethink the practice due to its dangers.

The 2019 death in Colorado of a young Black man named Elijah McClain brought scrutiny to the practice and led to a pair of paramedics being convicted for giving McClain an overdose of ketamine.

Overall, the practice of giving ketamine and other sedatives to people detained by police has spread quietly across the nation over the last 15 years, built on questionable science and backed by police-aligned experts, an investigation led by The Associated Press has found.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.