What is ketamine? A doctor explains the drug involved in Matthew Perry's death

More than a month after comedic actor Matthew Perry's unexpected death, the Los Angeles Medical Examiner's Office has released an autopsy report attributing his passing to an overdose of ketamine.

Perry, 54, was found unresponsive in his pool on on Oct. 28, "floating face down in the heated end," the report states. Contributing factors included drowning, coronary artery disease, and the presence of buprenorphine, a medication used to treat opioid addiction.

What is ketamine? The United States Drug Enforcement Administration lists ketamine as a hallucinogen. It is referred to as a "dissociative anesthetic hallucinogen" because it creates a feeling of detachment from pain and the environment.