Is Ketamine an Opioid?

By Pat Anson, PNN Editor

A drug used to treat depression and pain is being touted as possible solution to the opioid crisis.

This week a South Carolina drug maker said it would partner with a medical device company to sell ketamine in take home medication bags that can be administered by an ambulatory pain pump. The idea is to give patients recovering from surgery a safer alternative to opioids.

“We are proud to partner with InfuTronix Solutions to deliver opioid-free pain medication to patients across the country,” Nephron Pharmaceuticals CEO Lou Kennedy said in a statement. “The overuse of opioids is a crisis in America. Non-narcotic pain management is a cost-saving way that companies like ours can help save lives.”

Non-narcotic? Opioid-free?

That’s not what a team of researchers at Stanford University concluded last year after studying how ketamine works in the brain. In a small clinical study, they gave a dozen patients diagnosed with depression a combination of ketamine and naltrexone – an opioid-receptor blocker. To their surprise, naltrexone stopped ketamine from working as an antidepressant.

In effect, the researchers discovered that ketamine works just like oxycodone, hydrocodone and other painkillers – by activating opioid receptors in the brain. 

“Everything that I was taught, and everything that I’ve always taught my students — all of the evidence supports the fact that ketamine is not an opioid,” said lead author Boris Heifets, MD, a clinical assistant professor of anesthesiology, perioperative and pain medicine. “I was really surprised at the results.”

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“And the results were so clear that we ended the study early to avoid exposing additional patients to the ineffective combination treatment,” said co-lead author Nolan Williams, MD, a clinical assistant professor of psychiatry and behavioral science.

The Stanford research, published in The American Journal of Psychiatry, caught psychiatrists and pain management experts by surprise. Some urged caution about the long-term use of ketamine until more can be learned about potential side effects such as addiction. Some depressed patients taken off ketamine have shown signs of withdrawal and became suicidal.

“Given the rapid relapse and potential suicide risk, it is hard to know what to recommend to clinicians. Should they really continue to use the agent beyond an acute course? For how long? In whom?” Alan Schatzberg, MD, a Stanford professor of psychiatry and behavioral sciences, warned in a commentary. “The drug’s opioid properties need to be considered when considering how best to use it.”

‘A Black Eye to Ketamine’

Talk like that has given ketamine a bad rap, according to experts at Johns Hopkins University School of Medicine. They’ve published a commentary of their own, defending the use of ketamine as a necessary treatment for depression that doesn’t respond to typical antidepressants.

“A (Stanford) 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, MD, an assistant professor of psychiatry and behavioral sciences at Johns Hopkins.

“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.”

Kaplin says there is ample evidence that ketamine sticks to NMDA receptors in the brain that are involved in learning and memory. Because these NMDA receptors are found together with opioid receptors, Kaplin says it’s no surprise that the can meddle with one another, like interference picked up on a phone call or static on the radio.

“This interference and cross-talk does not mean that ketamine is an opioid, and to wrongly label it as such could eventually keep patients from essential antidepressant medications that could make a huge difference in their quality of life,” said Kaplin, who plans on opening a ketamine clinic.

The debate over whether ketamine is an opioid comes at a time when its use is expanding.  Ketamine was approved by the FDA in 1970 solely as a surgical anesthetic to be taken intravenously or by injection. But a growing number of clinics now offer off-label infusions of ketamine to treat depression, post-traumatic stress disorder and difficult chronic pain conditions such as Complex Regional Pain Syndrome (CRPS).

Demand has grown so much there are reports of ketamine shortages. Although ketamine itself is inexpensive, the infusions can cost several hundred dollars and are not covered by insurance.

Ketamine Nasal Spray

Not until this year did the Food and Drug Administration approve the use of ketamine to treat depression, when it okayed a nasal spray (Spravato) made by Janssen Pharmaceuticals that contains a ketamine compound.

The FDA approved Spravato even though 2 out of 3 short term trials failed to prove its effectiveness. The spray was effective in a longer trial, but only when taken with a conventional antidepressant.

Because of the risk of abuse and side effects, Spravato can only be administered in a doctor’s office, where patients can be observed for two hours after taking a dose. A single dose will cost about $900.

The FDA has called the herbal supplement kratom an opioid because it acts on opioid receptors, but the agency has not taken that step with ketamine. Given current attitudes about opioids, it’s fair to say the FDA would have never approved Spravato if it was considered an opiate.

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In addition to its medical uses, ketamine is used as a recreational party drug – known as “Special K” -- because it can cause hallucinations and intense dream-like states.

Whether taken to get high or to treat pain and depression, it’s clear that ketamine is a potent drug that has both harms and benefits. And experts say it needs to be viewed with caution until we know with more certainty how it works.

“Unfortunately, when one approaches ketamine as another antidepressant rather than a drug of abuse, this type of trap is easy to fall into, and in the end, such mistakes can be catastrophic,” Schatzberg said in his commentary. “We have witnessed four decades of supposedly new and safer opioids that have turned out often to be, if anything, even more abusable and lethal."