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MONDAY, August 2 (HealthDay News) -- The anesthetic drug ketamine helps ease depression in patients with treatment-resistant bipolar disorder, a new study finds.
Depressive symptoms are a major part of bipolar disorder, which affects about four percent of Americans at some point in their lives. There are several approved treatments for bipolar disorder, but some patients do not respond to these therapies.
Ketamine acts on the brain's glutamatergic system, which plays a role in information processing and memory formation. Recent research suggests that dysfunction in this brain system may contribute to bipolar disorder, noted Dr. Nancy Diazgranados and colleagues at the U.S. National Institute of Health.
Their study included 18 patients with bipolar depression that didn't improve when treated with the medications lithium or valproate. Two-thirds of the patients were on psychiatric disability and nearly all of them were unemployed.
The patients received an intravenous infusion of either ketamine or a placebo on two days two weeks apart. The order of the infusions was randomly assigned.
The patients' depressive symptoms were assessed before each injection and then 40, 80, 120 and 230 minutes, and one, two, three, seven, 10 and 14 days afterward. Within 40 minutes of receiving ketamine, the patients showed significant improvements in depressive symptoms compared to those who received the placebo. The improvements were most noticeable at day two and remained significant through day three.
At some point during the study, 71 percent of patients responded to ketamine and six percent responded to the placebo. No serious side effects were reported during the trial.
The study, published in the August issue of the journal Archives of General Psychiatry, provides evidence that the brain's glutamatergic system may play a role in bipolar disorder and that targeting it may lead to better treatments, the researchers wrote.
They also said that future research should explore how ketamine's rapid effect on depression can be maintained over the long-term.
Although ketamine has been used off-label as an experimental treatment for depression, it has not been approved by the U.S Food and Drug Administration for that use, according to the U.S. National Institutes of Health.
More information
The U.S. National Institute of Mental Health has more about bipolar disorder.
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