http://www.nytimes.com/2010/08/10/health/10depress.html
"Anesthetic Said to Aid Depression"
"A new study suggests that a 50-year-old drug commonly used as an anesthetic for humans and animals" —
"may deliver almost instant relief in some of the most troublesome cases of bipolar depression.
It has been known for several years that small doses of the drug, ketamine, can relieve major depression. But this study, done by researchers at the National Institute of Mental Health, is the first to demonstrate efficacy in patients with treatment-resistant bipolar depression.
Indeed, the researchers said, the effect on this group appeared to be even stronger. Although the study was small, with just 18 patients, it was conducted under the highest standards for a drug study: it was randomized, placebo-controlled and double-blinded.
In bipolar disorder, sometimes called manic-depressive illness, patients cycle between periods of elation and severe depression, and the depressive phase carries a high risk of suicide. It is commonly treated with mood stabilizers, including lithium, anticonvulsants and some antipsychotics, often in complex combinations.
Both mania and depression usually improve on these drugs. But when the depression remains, it is notoriously difficult to treat, so a fast-acting medicine with lasting effects would have obvious advantages. Ketamine probably acts by limiting the action of one type of brain receptor that moves nerve signals between neurons."