Ketamine was originally developed in the 1960s as an anaesthetic for use in surgery. It has become especially popular in the Third World as it can be given without a trained anaesthetist present - Ketamine, also known as 'K' or 'Special K', does not affect breathing and heart rate in the same way as other anaesthetics, which require careful monitoring of vital signs in case of any threat to life.

Animal studies have indicated that Ketamine can prevent brain damage like the damage that happens when you get a stroke. Many of the problems associated with strokes are actually caused by what happens afterwards. A chemical called glutamate is released in the brain. Brain cells then take this as a signal to explode and release more glutamate, causing more cells to die in a chain reaction known as 'glutamate cascade'.

Ketamine blocks a particular brain receptor called the NMDA receptor, which shuts off this chain reaction and thereby prevents brain damage. Although this protective effect has been demonstrated in animals, little work has been done in trying to administer Ketamine to humans suffering from strokes. And drug which hopes to minimise brain damage must generally be administered a short time after the stroke. But some physicians believe Ketamine is a promising treatment and the day may yet come when it is used to alleviate the long-term effects of strokes.

Recent research indicates that Ketamine is a highly promising treatment for long-term depression. A recent study saw 17 patients with depression given a dose of Ketamine. Within hours they reported relief from their symptoms. Current treatments for depression normally take several weeks or months to begin working.

This rapid effect has caused excitement in the medical community and may lead to many new treatments for depression. Dr Thomas Insel, director of NIMH, commented: "To my knowledge, this is the first report of any medication or other treatment that results in such a pronounced, rapid, prolonged response with a single dose. These were very treatment-resistant patients."

The same NMDA blocking effect that prevents stroke damage could be also be used to interrupt drug addiction, often associated with depression. Both Ibogaine and Harmaline (found in Ayahuasca) block the NMDA receptor like Ketamine, which seems to be one factor behind the addiction interrupting qualities of all three substances.

In Russia, scientists have for several years used Ketamine with some success to treat alcoholics and are now turning their attention to heroin addicts. It seems that Ketamine can interrupt addiction for many months after administration by psychotherapists and improve your chances of not relapsing back into addiction.

Ironically, K itself can be addictive. Ketamine aficionado DM Turner noted: "After about two years of once-per-week Ketamine use I found that I had developed an addiction... it took considerable effort to break the cycle of repeatedly using it, even though I was aware of detrimental effects that it was causing. Since that time I've used Ketamine only occasionally, but find that I must continually exercise a high degree of will power to prevent myself from falling into a pattern of regular use."

Both Ibogaine and Ayahuasca seem to have far less potential for addiction than Ketamine and are also being investigated by scientists as treatments for addicts.