As doctors in the United States reduce their use of opioid painkillers, another drug is becoming popular: ketamine.

For more than 50 years, ketamine has been used as a painkiller for patients having surgery. Now, for profit medical centers and online health services have increasingly used the drug as a treatment for pain, depression, anxiety and other conditions.

However, some experts worry about the increased use of the drug. They say there is not much research about how well the drug works to control pain. And they worry that, like opioids, too many patients may get prescriptions for it even though the drug carries safety and abuse risks.

Studying ketamine use

Dr. Padma Gulur is a pain specialist at Duke University in the state of North Carolina. She is studying ketamine's use. She says there are few pain medicines that doctors can choose from. So, limited research showing possible benefits of ketamine can lead to a big increase in its use, she told The Associated Press.

Gulur and her co-workers followed 300 patients receiving ketamine at Duke. They found that more than one-third of them reported important side effects that required professional help. These included hallucinations, troubling thoughts, and visual problems.

Ketamine also did not reduce opioid prescriptions in the months following treatment, Gulur said. The research is under review for publication.

Ketamine targets a brain chemical messenger called glutamate, which is thought to effect both pain and depression. A small amount of ketamine can produce strong effects on the brain, including hallucination.

Daniel Bass lives in the state of Kentucky. He was given ketamine for pain related to a rare bone and joint disorder. He said the drug reduced his pain, but the visual effects of the drug were "horrifying."

The business of ketamine

The U.S. Food and Drug Administration (FDA) approved ketamine 50 years ago as a painkiller for patients having surgery. The drug can now be purchased cheaply and prescribed by most doctors and some healthcare workers, like nurses, with less training.

Since 2017, prescriptions for ketamine have increased more than 500 percent, Epic Research, a medical data company said. Pain was the top condition for which ketamine was prescribed, though depression has been rising quickly.

Dr. David Mahjoubi owns the Ketamine Healing Clinic in Los Angeles, California. He offers ketamine for several conditions including pain, alcohol addiction and anxiety. "We want patients to disassociate or feel separate from their pain, depression or anxiety," he said. "If they feel like they're just sitting in the chair the whole time, we actually give them more."

Doctors can buy ketamine for less than $100 per treatment. They then charge between $500 and $1,500 to inject patients with the drug.

Online prescriptions have also become easier since COVID-19. So, health centers face increasing competition from online health services like MindBloom and Joyous. These companies connect patients with doctors who can prescribe mixed versions of ketamine, like nasal spray and pills, remotely and send it through the mail.

In May, health officials tried to end the policy permitting online prescriptions of high-risk drugs like ketamine and opioids. But they agreed to extend the policy through 2024 after pushback from online health companies and doctors.

Dr. Samuel Wilkinson is a Yale University psychiatrist who prescribes ketamine and other drugs for depression. He says the current rules for prescribing ketamine are not very strict. "There's good things about that and not-so-good things about that," he said.

Last month, the FDA warned doctors and patients against mixed versions of ketamine. The agency said it does not regulate what goes into the mixtures and cannot say if they are safe. The warning followed a similar one last year about nasal spray versions of ketamine.

For now, experts say it is unlikely health officials will go beyond their recent warnings about mixtures of the drug.

Dr. Caleb Alexander is a drug safety researcher at Johns Hopkins University. He said controlling health centers is beyond the power government officials currently have.

I'm Andrew Smith. And I'm Faith Pirlo.

Matthew Perrone wrote this story for the Associated Press. Andrew Smith adapted it for VOA Learning English.

________________________________________________

anxiety -n. a feeling of worry or nervousness

prescription -n. a signed order from a medical professional for medicine a patient can take

benefit -n. a good or positive effect or result

hallucination -n. a mental state of seeing something that is not really there, usually because you are ill or have taken a drug.

visual -adj. related to vision, or seeing

under review -adj. phrase; to be looked at and checked carefully

horrifying -adj. producing strong feelings of fear or extremely upsetting

addiction -n. a condition of taking harmful drugs and being unable to stop taking them

version -n. a particular form or type of something