 Ketamine is an intravenous anesthetic with analgesic properties in subanesthetic doses. Ketamine is a noncompetitive antagonist of N-methyl-D-aspartate NMDA receptors. NMDA receptors are involved in central pain sensitization via wind-up phenomenon and altered pain memory, a process which can be blocked by ketamine. NMDA receptor antagonists may prevent the development of tolerance to opioids and hyperalgesia. Ketamine has been safely used to decrease pain in numerous studies. Ketamine can also act as an antidepressant with hours of administration. 