In a small study, the drug ketamine eased depression in patients with bipolar disorder, often in as little as 40 minutes.
Within 40 minutes of receiving a ketamine injection, over half the subjects reported at least a 50% reduction in depression. And 13% became nearly symptom-free. This response lasted about three days on average and peaked on day two.
Overall, 71% of the subjects responded positively to ketamine at some point in the study, while only 6% did so to a saline injection.
Even if ketamine does not end up being a useful medication for treating bipolar disorder or depression, it is likely to point the way to other medications that will be.
The suicide rate for people with bipolar disorder is among the highest for any psychiatric disorder. A faster acting medication would be enormously useful.
The ketamine study was performed on 18 people whose bipolar disorder had not been helped by other medications. People were given an injection of either ketamine (0.5 mg/kg body weight) or salt solution. Two weeks later, each person was given whichever type of injection they did not receive the first time.
The effects on depression were measured from the subjects' responses to a depression questionnaire called the Montgomery-Asberg Depression Rating Scale. This was given at the start of the study and at various times during the first six hours after injection, as well as 1, 2, 3, 7, 10 and 14 days after each injection.
All subjects were taking either lithium or valproate for their bipolar disorder at the start of the study and continued to take them throughout the study.
Ketamine is known to bind to specific glutamate receptors (NMDA receptors) in the brain, lowering the amount of glutamate that can bind to them. Glutamate is a neurotransmitter, a chemical that transmits signals between nerves. This suggests that other drugs which target glutamate receptors may also offer the kind of fast acting relief seen in the ketamine study.
An article detailing the study was published in the August 2010 issue of Archives of General Psychiatry.