Ketamine has gotten a bad rap as an opioid when there’s plenty of evidence suggesting it isn’t one, Johns Hopkins experts say. They believe this reputation may hamper patients from getting necessary treatment for the kinds of depression that don’t respond to typical antidepressants. In a new paper, the researchers clarify the mechanism behind ketamine’s mechanism of action in hopes of restoring the therapy’s standing among health care professionals and the public.
In March of this year, the U.S. Food and Drug Administration approved ketamine as a nasal spray to treat depression.
“A study done late last year delivered a black eye to ketamine, and as a result of the coverage, there was a wholesale acceptance by both potential patients and physicians that ketamine is an opioid,” says Adam Kaplin, M.D., Ph.D., assistant professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine. “This is most worrisome if people continue to think this way, particularly in the wake of the opioid epidemic; clinicians won’t refer patients for a treatment, despite that it has been shown to be incredibly effective for many patients with treatment-resistant depression.”
The researchers published their viewpoint and explanation of the alternative mechanism as a Letter to the Editor in the May 1 issue of the American Journal of Psychiatry.
Naltrexone—the drug used to reverse accidental opioid overdoses—binds to opioid receptors on the surface of brain cells and prevents opioids like morphine or heroin from sticking to them and acting on the brain, preventing the high.
How Does Ketamine Work?
In late 2018, researchers at Stanford University and Palo Alto University showed that naltrexone also blocks the antidepressant effects of ketamine, which led them to propose that ketamine must also bind to the same opioid receptors and thus concluded that ketamine must be an opioid. Kaplin says that there’s plenty of contrary evidence demonstrating that ketamine sticks to an entirely different receptor on brain cells: the NMDA receptors—involved in learning and memory—instead of the opioid receptors.
Learn more at https://medicalxpress.com/news/2019-07-ketamine-isnt-opioid-depression-unique.html
