For people struggling with severe depression, antidepressants have the potential to provide much-needed relief, but they often take weeks to work. That’s why there is growing excitement about reports that the anesthetic drug ketamine, when delivered intravenously in very low doses, can lift depression and suicidal thoughts within a matter of hours. Still, there has been reluctance to consider ketamine for widespread treatment of depression because, even at low doses, it can produce very distressing side effects, such as dissociation—a sense of disconnection from one’s own thoughts, feelings, and sense of identity. Now, new findings suggest there may be a way to tap into ketamine’s depression-fighting benefits without the side effects.
In a mouse study published in the journal Nature, an NIH-funded research team found that the antidepressant effects of ketamine are produced not by the drug itself, but by one of its metabolites—a substance formed as the body breaks ketamine down. What’s more, the work demonstrates that this beneficial metabolite does not cause the risky dissociation effects associated with ketamine. While further development and subsequent clinical trials are needed, the findings are a promising step toward the development of a new generation of rapid-acting antidepressant drugs.
Ketamine belongs to a class of drugs that block neurochemical receptors found on nerve cells called NMDA receptors, or NMDARs. These receptors respond to the chemical messenger known as glutamate, helping to form and maintain neural connections and play a role in memory. It wasn’t clear, however, that this action of ketamine could explain its effects on depression, since clinical trials of other drugs targeting NMDARs failed to show the same antidepressant effects.
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