Because of its hallucinatory effects, the drug also became a popular club drug among recreational users under the names "K", "Ket", "Special K", and "Vitamin K".  Most of the illegal ketamine coming into the U.S. comes across the Mexican border, according to recent studies.  The drug has risen greatly in popularity over the last decade and is taken by itself or in mixes with other drugs.  One common mixture is Ecstasy (MDMA), Ketamine and other additives; names for these kind of mixes include "Strawberry" and "Sitting Duck".

While the effects of recreational ketamine have remained mostly unknown, a new study by the University College London has linked the drug to memory problems and has raised concerns both about its legal and illegal uses.  Previous studies had implicated the drug with kidney and bladder damage, but hadn't shown significant evidence of mental effects.

The new study involved psychological tests being performed on 120 people, some of which were frequent users.  Researchers found that the users had difficulty with memory-related chores, such as recalling names, conversations and patterns.  While it was possible that the results were skewed by the use of other drugs (e.g. MDMA), there appeared to be a clear link between ketamine abuse and memory problems.  The study helped reduce false positives based on other usage by splitting the participants into five groups -- those who used ketamine every day, recreational users who took the drug once or twice a month, former users, those who used other drugs, and people who did not take any drugs.

Frequent users of the drug made as many as twice as many mistakes on the test, and a followup which took place a year later.  The users' performance worsened from the initial study to the followup, indicating the drug was deteriorating brain function.  The other groups, including those that used other drugs (which presumably included MDMA) did not show significant differences memory problems.  Intriguingly, those on ketamine also showed growing signs of unusual beliefs or mild delusions, such as conspiracy theories in their psychological evaluations.

The study also showed signs that the drug was addictive.  Hair tests showed that users were taking twice the amount of ketamine they initially were, a year later.  The need to increase the regularity or amount of drug dosing is a hallmark sign of addiction to a substance.  Lead researcher Dr Celia Morgan comments, "Ketamine use is increasing faster than any other drug in the UK, particularly among young people, and has now become a mainstream club drug.  However, many young people who use this drug may be largely unaware of its damaging properties and its potential for addiction. We need to ensure that users are informed of the potentially negative consequences of heavy ketamine use."

Ketamine can be purchased illegally at lower prices, thanks to falling prices in the U.S., UK, and elsewhere.  A gram is estimated to cost approximately £20 in the UK ($33), less than half the price of a gram of cocaine.  With abuse on the rise, both the U.S. and UK have recently moved to class the drug as a controlled substance, making it a crime to purchase the drug without a prescription or to try to sell it outside the medical system.  In the U.S. the United States Controlled Substance Act of 1999 classed it as a Schedule III drug -- the same class given to codeine/hydrocodone.  In the UK it similar was made illegal for recreational use three years ago and classed as a Class C drug.

Unfortunately, some patients legally rely on the drug for pain relief.  The results raise greater questions about whether ketamine prescription is wise, though, versus alternatives.

The new research was published in the advance copy of the Addiction journal, a psychological journal published on the behalf of the Society for the Study of Addiction.