Multiple arrests have been made and federal charges filed in connection with "Friends" actor Matthew Perry's October ketamine death, ABC News has learned.
The arrests were made in an early morning operation, and charges will be announced at a news briefing on Thursday with the U.S. Attorney for Los Angeles and the DEA Administrator. Five people -- including two doctors -- have been charged with conspiracy to distribute ketamine, according to a federal source.
The charges will also include the death of another person who is referred to in the indictment by the initials C.M., according to the federal source.
An autopsy report from the Los Angeles County coroner in December named acute effects of ketamine as the cause of death for Perry.
According to the report, Perry reportedly was on ketamine infusion therapy and had a ketamine infusion one and a half weeks before his death. However, the medical examiner concluded that the ketamine in his system could not have been from that infusion, as ketamine has a half-life of three to four hours or less.
The report also listed drowning, coronary artery disease, and buprenorphine effects as contributing factors not related to the immediate cause of death. Perry's death was ruled an accident.
Buprenorphine is a medication used to treat Opioid Use Disorder, according to the Substance Abuse and Mental Health Services Administration.
Here is a look at what ketamine is and how it is used in medical treatment.
MORE: What you need to know about ketamine therapyKetamine is part of a class of medications called dissociative anesthetics.
"It can interrupt a person's perception of the reality and what that looks like is when someone might be awake but not fully conscious," ABC News medical correspondent Dr. Darien Sutton explained on "Good Morning America" Monday.
Ketamine may be used medically to induce anesthesia. In more recent years, it's also been used for treatment-resistant depression, according to StatPearls, an online library published in the National Library of Medicine.
"Ketamine, at low doses, can be prescribed. It's most often used in a clinical setting under close cardiac monitoring," Sutton explained.
"In terms of using it with someone who might have a history of substance use disorder, it also has been studied for the use of substance use disorders and found benefits. For example, ketamine has been shown to be beneficial in helping patients decrease their cravings and helping them with abstinence away from drugs," Sutton continued.
Ketamine has a "potential for recreational misuse," according to American Addiction Centers.
"It can negatively affect your heart rate, your blood pressure, it can cause deep levels of sedation and even stop breathing and for these reasons are reasons why it needs to be always be used under the close monitoring management of a medical professional," Sutton said.
"The use of ketamine recreationally or anything outside of a prescription can cause danger," Sutton added. "Ketamine can cause you to be in a vulnerable state where you might be at harm, at risk from your environment. And it also, again, causes deep levels of sedation and you just don't know exactly how much is in whatever dose you have so you always have to pay attention and again, consult a medical professional."
According to the Drug Enforcement Agency, ketamine was approved in the 1970s as a rapid-acting anesthetic by the U.S. Food and Drug Administration.
In recent years, off-label ketamine has been used to treat psychological disorders like depression and PTSD.
"The average antidepressant takes about two months to produce a reduction in symptoms," Dr. John Crystal, co-director of the Yale Center for Clinical Investigation, told ABC News' Eva Pilgrimin November. "Ketamine produces those same kinds of improvements within 24 hours in many people."
Ketamine therapy made headlines in 2021 when former NBA player Lamar Odom opened up to "Good Morning America" about his use of the drug therapy to help him battle addiction. "I went to rehab and did some other things, but ketamine came into my life at the right time," Odom told ABC News' Steve Osunsami.
"I think of ketamine as an intervention that is part of an overall treatment," said Crystal. "Ketamine can be something that can facilitate and enhance the impact of psychotherapy."
"Death by ketamine overdose rarely occurs if ketamine is the only drug someone takes," according to American Addiction Centers.
MORE: Can ketamine be effective in treating diagnosed depression?The lethal dose of ketamine is estimated to be about 5.6 milligrams per pound for a 154-pound human, according to the StatPearls journal in the National Library of Medicine.
Beyond the risk of death, Dr. John Crystal, co-director of the Yale Center for Clinical Investigation, told Eva Pilgrim in November that ketamine therapy should not be used by people with schizophrenia or people who are developing a psychiatric illness.