The increase in recreational use prompted ketamine to be placed in Schedule III of the United States Controlled Substance Act in August 1999. Recreational use
At sub-anesthetic doses ketamine produces a dissociative state, characterised by a sense of detachment from ones physical body and the external world that is known as depersonalization and derealization. At sufficiently high doses, users may experience what is called the "K-hole", a state of dissociation with visual and auditory hallucination. John C. Lilly, Marcia Moore, D. M. Turner, and David Woodard (amongst others) have written extensively about their own entheogenic and psychonautic experiences with ketamine. Turner died prematurely due to drowning during presumed unsupervised ketamine use. In 2006 the Russian edition of Adam Parfreys Apocalypse Culture II was banned and destroyed by authorities owing to its inclusion of an essay by Woodard about the entheogenic use of, and psychonautic experiences with, ketamine. : 288–295 
Recreational ketamine use has been implicated in deaths globally, with more than 90 deaths in England and Wales in the years of 2005–2013. They include accidental poisonings, drownings, traffic accidents, and suicides. The majority of deaths were among young people. Because of its ability to cause confusion and amnesia, ketamine has been used for date rape. Research
Ketamine is under investigation for its potential in treating treatment-resistant depression.. Ketamine is a known psychoplastogen, which refers to a compound capable of promoting rapid and sustained neuroplasticity.A phase 2 clinical study showed that ketamine can safely and effectively reduce levodopa-induced dyskinesia in patients with Parkinson’s disease.
Relationships between levels and effects
Dissociation and psychotomimetic effects are reported in people treated with ketamine at plasma concentrations of approximately 100 to 250 ng/mL (0.42–1.1 μM). The typical intravenous antidepressant dosage of ketamine used to treat depression is low and results in maximal plasma concentrations of 70 to 200 ng/mL (0.29–0.84 μM). At similar plasma concentrations (70 to 160 ng/mL; 0.29–0.67 μM) it also shows analgesic effects. In 1–5 minutes after inducing anesthesia by a rapid intravenous injection of ketamine, its plasma concentration reaches as high as 60–110 μM. When the anesthesia was maintained using nitrous oxide together with continuous injection of ketamine, the ketamine concentration stabilized at approximately 9.3 μM. In an experiment with purely ketamine anesthesia, people began to awaken once the plasma level of ketamine decreased to about 2,600 ng/mL (11 μM) and became oriented in place and time when the level was down to 1,000 ng/mL (4 μM). In a single-case study, the concentration of ketamine in cerebrospinal fluid, a proxy for the brain concentration, during anesthesia varied between 2.8 and 6.5 μM and was approximately 40% lower than in plasma. Pharmacokinetics
Ketamine can be absorbed by many different routes due to both its water and lipid solubility. Intravenous ketamine bioavailability is 100% by definition, intramuscular injection bioavailability is slightly lower at 93%, and epidural bioavailability is 77%. Subcutaneous bioavailability has never been measured, but is presumed to be high. Among the less invasive routes, the intranasal route has the highest bioavailability (45–50%) and oral – the lowest (16–20%).