Ketamine is an FDA-approved synthetic narcotic medication that medical professionals have used for decades to provide pain relief and as an intravenous anesthetic. The drug is now used to treat addiction, anxiety, depression, obsessive-compulsive disorder, post-traumatic stress disorder, as well as for chronic pain and conditions such as fibromyalgia. In addition, the intranasal form of esketamine, branded as Spravato or by other names, is approved for treatment-resistant depression.