New York, May 11 (IANS) Low doses of a general anaesthetic drug is likely to reduce suicidal thoughts in patients with treatment-resistant depression, finds a new study.

The findings showed that repeatedly infusing low doses of ketamine in depressed patients with recurrent suicidal thoughts might help them in recovering rapidly. 

"Our finding that low doses of ketamine, when added on to current antidepressant medications quickly decreased suicidal thinking in depressed patients, is critically important because we don't have many safe, effective and easily available treatments for these patients," said Dawn Ionescu, lead researcher from Massachusetts General Hospital (MGH) in the US.

Having suicidal thoughts increases the risk that patients will attempt suicide. However, the risk of suicide attempts is 20 times higher in patients with depression than the general population. 

The study, published online in the Journal of Clinical Psychiatry, was designed not only to examine the antidepressant and anti-suicidal effects of repeated low-dose ketamine infusions, but also to examine the safety of increased ketamine dosage.

The team enrolled 14 patients with moderate to severe treatment-resistant depression who had suicidal thoughts for three months or longer and they received two weekly ketamine infusions over a three-week period. 

The initial dosage administered was 0.5 mg/kg over a 45-minute period -- about five times less than a typical anaesthetic dose -- and after the first three doses, it was increased to 0.75 mg/kg. 

The participants were assessed on measures of suicidal thinking, in which patients were directly asked to rank whether they had specific suicide-related thoughts, their frequency and intensity.

The results showed that most of them experienced a decrease in suicidal thinking, and seven achieved complete remission of suicidal thoughts at the end of the treatment period. 

"The study that aim to understand the mechanism by which ketamine and its metabolites work for people with suicidal thinking and depression may help us discover areas of the brain to target with new, even better therapeutic drugs," Ionescu concluded.​