Ketamine, sold under the brand name Ketalar among others, is a medication mainly used for starting and maintaining anesthesia. It induces a trance-like state while providing pain relief, sedation, and memory loss. Other uses include for chronic pain and for sedation in intensive care. Heart function, breathing, and airway reflexes generally remain functional. Effects typically begin within five minutes when given by injection with the main effects lasting up to 25 minutes.
Common side effects include psychological reactions as the medication wears off. These reactions may include agitation, confusion, or hallucinations. Elevated blood pressure and muscle tremors are relatively common, while low blood pressure and a decrease in breathing are less so. Spasms of the larynx may rarely occur. Ketamine has been classified as an NMDA receptor antagonist but its mechanism was not well understood as of 2017.