Researchers cautioned that the existing evidence base is too poor to draw any solid conclusions on whether ketamine can help patients suffering from chronic pain.
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Ketamine has taken off among the experimental wellness crowd in recent years, its image transforming from party drug to potential salve for mental health problems and long-lasting pain.
The anaesthetic has long been used to sedate people for surgery and as an emergency painkiller. More recently, scientists have also explored it as a treatment for chronic pain and depression, with ketamine clinics cropping up across Europe.
But a major new review found there is no evidence that ketamine actually works to alleviate chronic pain.
Ketamine can, however, come with a slew of side effects, particularly when it’s given through a vein. That includes delusions, delirium, paranoia, nausea, and vomiting, according to the analysis, which was carried out by Cochrane, an influential nonprofit research group.
The researchers concluded that the existing evidence base is too poor to draw any solid conclusions on whether ketamine can help patients suffering from chronic pain.
“We want to be clear – we're not saying ketamine is ineffective, but there’s a lot of uncertainty,” Michael Ferraro, one of the review’s authors and a researcher at the University of New South Wales (UNSW), said in a statement.
“The data could point to a benefit or no effect at all. Right now, we just don’t know,” he added.
Ferraro’s team analysed data from 67 clinical trials involving more than 2,300 people. It assessed five drugs that target the N-methyl-D-aspartate (NMDA) receptor, which affects how people experience pain.
The drugs, known as NMDA receptor antagonists, are thought to reduce pain by blocking certain signals in the brain. Included in the review were ketamine, memantine, dextromethorphan, amantadine, and magnesium.
The review looked at multiple dosing strategies and health conditions that cause chronic pain, such as diabetic nerve pain, postshingles pain, fibromyalgia, and complex regional pain syndrome.
While there was no clear evidence of any benefits from ketamine or the other drugs, their side effects of ketamine were “distressing for many patients,” Ferraro said.
Notably, there were no trials that looked at how well ketamine worked for patients with depression or as a substitute for opioid painkillers, the review found.
The researchers warned doctors against prescribing ketamine to chronic pain patients based on the fact that the drug can help people in need of short-term relief, for example in the emergency room.
“We've seen the harm that can come from taking medicines developed for acute pain and applying them to chronic pain, opioids are a prime example. Now we're seeing a similar pattern with ketamine,” said James McAuley, one of the review’s authors and a UNSW professor.
“We need to be careful not to rush into widespread use without strong evidence,” he added.