JUL 31, 2019 06:30 PM PDT

Ketamine is not an opioid, and treats depression in a novel way

In March, the U.S. Food and Drug Administration approved ketamine nasal spray to treat depression. Ketamine has gotten a bad rap as an opioid - which it is not - despite solid scientific evidence suggesting that it isn't one.

According to Adam Kaplin, M.D., Ph.D., an assistant professor of psychiatry and behavioral sciences at Johns Hopkins School of Medicine, both patients and physicians tend to perceive ketamine as an opioid. "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 treatment, despite that it has been shown to be incredibly effective for many patients with treatment-resistant depression," says Kaplin.

Researchers published their viewpoint and explanation of the drug's mechanism as a Letter to the Editor in the American Journal of Psychiatry

Naltrexone - a drug used to treat opioid addiction by preventing opioid effects (e.g. feelings of well-being, pain relief) - binds to opioid receptors on brain cells and prevents other opioids like heroin from binding. In 2018, a study showed that naltrexone also blocks the antidepressant effects of ketamine, which led researchers to conclude that ketamine may also bind to opioid receptors. But this is not true. According to Kaplin, ketamine actually binds primarily to an entirely different set of receptors: the NMDA receptors - important for learning and memory - rather than the opioid receptors.

Normally, NMDA receptors are activated by the chemical glutamate. Turning on these receptors turns off a master control switch in the cell called mTOR, which ultimately is in charge of creating new memories. Ketamine also binds to the NMDA receptors, but it has the opposite effect in that it turns these receptors off. Turning off NMDA receptors turns on the mTOR switch, which is required for the drug's antidepressant effects.

The "ketamine as an opioid" misconception is all about mTOR. Opioid receptors in the brain are actually always turned on at low-levels, even in the absence of a drug. This low activity suppresses a chemical called cyclic AMP (cAMP). When the drug naltrexone is administered, it binds to opioid receptors, thereby increasing cAMP. Remember, ketamine turns on mTOR, which enables antidepressant effects; but if naltrexone is given in addition to ketamine, mTOR is shut down again. This is why naltrexone overrides the antidepressant effects of ketamine.

Although NMDA receptors are found together with opioid receptors in the brain, and their components can meddle with each other, this does not mean that ketamine is an opioid, says Kaplin.

In a more psychological or behavioral sense, another reason ketamine should not be considered an opioid because it actually does not have the same addictive potential as opioids. The FDA specified that ketamine is to be administered under the watch of physicians in small doses and in a controlled clinical setting to minimize any chance of abuse. The drug works much faster than traditional antidepressants, sometimes even after just one or two uses, which also decreases the risk of abuse.

Source: ScienceDaily, Medical Express

 

 

About the Author
You May Also Like
SEP 22, 2019
Genetics & Genomics
SEP 22, 2019
Investigating Previously Unmapped Regions of the Human Genome
Researchers have used cutting edge imaging tools to map a region of the human genome that has not been well-described....
SEP 22, 2019
Health & Medicine
SEP 22, 2019
Are You Getting Enough Heart-Healthy Sleep?
Is there a sleep duration sweet spot to decrease your risk of heart attacks? According to researchers from the University of Colorado: Boulder, there is! T...
SEP 22, 2019
Genetics & Genomics
SEP 22, 2019
A 3D Look at the Genome Reveals a Super Enhancer
We can write out the sequence of the genome, but the three-dimensional structure of the molecule is important to its function as well....
SEP 22, 2019
Cardiology
SEP 22, 2019
Hula Dancing Helps Hawaiians Lower Blood Pressure
The rates of stroke and heart disease are about four times higher for Native Hawaiians than for non-Hispanic whites, according to EurekAlert. Can a traditi...
SEP 22, 2019
Drug Discovery & Development
SEP 22, 2019
How Does Ketamine Treat Depression?
In recent years, ketamine has received growing interest for its neuroprotective effects. Known to alleviate symptoms of depression in just hours whereas co...
SEP 22, 2019
Cardiology
SEP 22, 2019
The WHO Reemphasizes The Importance Of Nutrition
Nutrition lies at the foundation of good health. Without adequate nutrients, people are at substantially elevated risk for developing health problems. The...
Loading Comments...