Ketamine is a drug used in human and veterinary medicine. Its hydrochloride salt is sold asKetanest, Ketaset, and Ketalar.
Pharmacologically, ketamine is classified as an NMDA receptor antagonist. At high, fully anesthetic level doses, ketamine has also been found to bind to opioid µ receptors and sigma receptors. Like other drugs of this class such astiletamine and phencyclidine (PCP), it induces a state referred to as “dissociative anesthesia” and is used as a recreational drug.
Ketamine produces effects similar to phencyclidine (PCP) and dextromethorphan (DXM). Unlike the other well known dissociatives PCP and DXM, ketamine is very short acting, its hallucinatory effects lasting sixty minutes when insufflated or injected and up to two hours when ingested, the total experience lasting no more than a couple of hours. Like other dissociative anaesthetics, hallucinations caused by ketamine are fundamentally different from those caused by tryptamines and phenethylamines. At low doses, hallucinations are only seen when one is in a dark room with one’s eyes closed, while at medium to high doses the effects are far more intense and obvious.
Ketamine produces a dissociative state, characterised by a sense of detachment from one’s physical body and the external world which is known as depersonalization and derealization. At sufficiently high doses (e.g. 150 mg intramuscular), users may experience what is coined the “K-hole”, a state of dissociation whose effects are thought to mimic the phenomenology of schizophrenia. Users may experience worlds or dimensions that are ineffable, all the while being completely unaware of their individual identities or the external world. Users have reported intense hallucinations including visual hallucinations, perceptions of falling, fast and gradual movement and flying, “seeing God”, feeling connected to other users, objects and the cosmos, experiencing psychotic reactions, and shared hallucinations, and thoughts with adjacent users.
Users may feel as though their perceptions are located so deep inside the mind that the real world seems distant (hence the use of a “hole” to describe the experience). Some users may not remember this part of the experience after regaining consciousness, in the same way that a person may forget a dream. Owing to the role of the NMDA receptor in long-term potentiation, this may be due to disturbances in memory formation. The “re-integration” process is slow, and the user gradually becomes aware of surroundings. At first, users may not remember their own names, or even know that they are human, or what that means. Movement is extremely difficult, and a user may not be aware that he or she has a body at all.
Chronic use of ketamine may lead to cognitive impairments including memory problems, and Ketamine is considered one of the few addictive psychedelics.
Ketamine can bring about both physical and psychological symptoms of withdrawal. These may include anxiety, insomnia, paranoia, seizures, as well as depression.