The nonmedical use of ketamine, part two: A review of problem use and dependence.

This is the second part of a review of the nonmedical use of ketamine. Part one discussed the history of ketamine, the sought-after effects for which it is taken in a nonmedical context, how these are produced, common adverse effects, the ketamine schizophrenia model and the neurotoxicity issue. Part two reviews what is currently known about problem use of ketamine, ketamine dependence, treatment options and harm minimization issues. Some ketamine users become dependent on the drug in a manner resembling cocaine dependence, with craving and a high tolerance but no evidence of a physiological withdrawal syndrome. The likely mechanisms of this dependence are discussed in terms of what is known about the neurochemistry of ketamine, its psychological effects, and published case histories in both the formal and informal literature. The conclusions are that ketamine dependence is linked with effects that this complex drug has in common with not only cocaine and amphetamine but also with opiates, alcohol and cannabis, as well as the psychological attractions of its distinctive psychedelic properties.