Ketamine is a dissociative anesthetic used legally in both human and veterinary medicine for inducing a loss of consciousness and pain relief. It is also used “off-label” in clinical settings for various conditions, including treatment-resistant depression and chronic pain, but it is a Schedule III controlled substance due to its potential for misuse as a recreational drug. 
Medical Uses
Ketamine is valued in medicine for its ability to provide strong analgesia (pain relief) and sedation without significantly suppressing essential protective reflexes like breathing or the airway reflex, making it particularly useful in emergency and battlefield settings. 
Anesthesia and Pain Management: It is FDA-approved as a general anesthetic for diagnostic and surgical procedures, especially in children or patients where IV access is difficult. It can also be used for acute and chronic pain management, sometimes as an opioid-sparing technique.
Mental Health Treatment: A derivative of ketamine, esketamine (brand name Spravato®), is an FDA-approved nasal spray used in combination with an oral antidepressant for adults with treatment-resistant depression. Ketamine itself is also used off-label for a range of mental health conditions, including anxiety disorders, PTSD, and suicidal ideation, with rapid, though often short-lived, positive effects.