Abuse of ketamine, a powerful anesthetic, is on the rise in many countries and now new research shows that repeated use of the club drug impairs memory, concentration, and psychological well-being.

Ketamine, sometimes called Special K on the street, is mostly used as a veterinary anesthetic. In humans, it causes hallucinations and high blood pressure.

A one-time dose of ketamine can cause psychosis-like effects and impaired thinking, Dr. Celia J. A. Morgan and colleagues, from University College London, note in the journal Addiction. The impact of long-term, repeated use of the drug, however, was unclear.

In the first ever large-scale, forward-looking study of ketamine abuse, Morgan’s team followed 150 people for over 1 year to assess how use of the drug affects memory, concentration, and psychological well-being.

The subjects were evenly divided into five groups based on their usage of ketamine: nearly daily use in large quantities (frequent use), use once or twice a month (recreational use), former use, use of illicit drugs other than ketamine, and no use of any illicit drugs. A variety of standard tests were used to assess their thinking ability and psychological well being.

Impairments in thinking ability and psychological well-being were mostly seen in frequent users. Moreover, as the study year progressed, short term memory and visual memory continued to worsen in this group.

Frequent ketamine users also had disturbances in verbal memory, such as forgetfulness and difficulty in recalling people’s names or conversations.

By contrast, recreational ketamine users and former users did not show disturbances in memory, attention, or most tests of psychological well-being, suggesting that occasional use does not cause lasting damage and that the impairments seen may be reversible when usage is stopped. Nonetheless, these users, as well as frequent users, showed evidence of having mild delusions.

Testing of hair samples revealed ketamine levels doubled in recreational users during the course of the study, a pattern that has been observed with other addictive drugs. No marked change was noted in frequent users, but this was likely because their levels were already very high when the study began.

“Despite the dramatic increase in ketamine use over the past decade, young people who use this drug are still largely unaware of its damaging health properties and its potential for dependency,” the researchers state. “Health education campaigns should target ketamine users to ensure that people are informed of the negative consequences of heavy ketamine use.”

SOURCE: Addiction, November 16th online issue, 2009.