Ketamine is a medication mainly used for starting and maintaining anesthesia. It induces a trance-like state while providing pain relief, sedation, and memory loss. Ketamine may be used for postoperative pain management. Low doses of ketamine may reduce morphine use, nausea, and vomiting after surgery. It may also be used as an intravenous analgesic with opiates to manage otherwise intractable pain, particularly if this pain is neuropathic. It has the added benefit of counteracting spinal sensitization or wind-up phenomena experienced with chronic pain. At these doses, the psychotropic side effects are less apparent and well managed with benzodiazepines.
Ketamine has been tested as a rapid-acting antidepressant for treatment-resistant depression in bipolar disorder, and major depressive disorder. Ketamine's antidepressant effect has a short duration of action. Meta-analyses have shown overwhelming clinical evidence to support the acute efficacy of ketamine in severely unwell populations, but a lack of data on optimal dosing and the effect of long-term treatment. Currently, ketamine is not approved for the treatment of depression, and so this is an off-label use.