Ketamine, a drug traditionally used as an anaesthetic, could be used to avert suicide and treat depression, according to a study at the University of New South Wales.

"This is a game-changer in treating depression," said Professor Colleen Loo, who is the lead author of the study, in a statement. "The real advantage here is that the effect is almost instantaneous and that it appears to work on the majority of patients."

Researchers said that the conventional anti-depressants take at least eight weeks to be active and productive. And then finding the right drug based on trial and error methods could take a bit longer.

Ketamine can help provide relief to patients by reducing their suicidal thoughts faster than the traditional medication. The drug can be used in combination with other anti-depressants to maintain sleep and appetite.

"Ketamine powerfully reverses structural changes in the brain that occur when someone is depressed. In a sense, the treatment is repairing or reversing those changes," Loo said.

Ketamine - which is also known as "special K" - has found to be temporarily effective in most patients who were part of the trial. The participants were suffering from Major Depressive Disorder and had undergone all other existing medical treatments.

In the study conducted at the Wesley Hospital, Sydney, three or four patients displayed an anti-depressant response following just one treatment session. However, they relapsed in a week's time. The researchers suggested that some patients might require lower dosage to reduce side-effects like altered perception and hallucinations.

Researchers said that although the study included a small group of participants, the results are significant.

The findings have been published in the World Journal of Biological Psychiatry.