A third of people who underwent weight-loss surgery at University of Michigan Health from 2018 to 2020 were at high risk of overdosing from prescription drugs, as measured by an algorithm from the state's prescription monitoring program, new research found.

After their operations, these at-risk patients were much more likely to be prescribed a secondary opioid (a different drug from the one given to help them deal with post-surgical pain) than patients at lower risk of overdose.

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Patients with high overdose risk scores were also more likely to have been diagnosed with a mental health condition and to go to the emergency room for issues that didn't require hospitalization.

People who are obese often experience chronic pain – and are more likely to be prescribed opioids to help them cope with that pain. 

But previous U-M-led research found that it's also common for patients who undergo bariatric surgery to begin using opioids on a regular basis for the first time after their weight-loss operation.

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As a result, the bariatric surgery team at U-M Health had been trying to reduce the amount of opioids they prescribed and thought that determining overdose risk would provide some helpful context for those efforts.

"We recognized that there's obesity related to pain syndromes that we wanted to address in a patient-centric way," said Oliver Varban, M.D., the co-director of the adult bariatric surgery program at University of Michigan Health and an associate professor of surgery at the University of Michigan Medical School. "We wanted to be able to measure that and to provide the appropriate resources for at-risk patients in the context of doing an operation that would improve their overall health."

How to measure overdose risk

Varban and his colleagues used NARxCHECK (abbreviated as Narx) scores developed by the state's prescription drug monitoring program to assess the overdose risk of each patient they studied. 

These scores, which range from 0 to 999, are based on a wide range of factors, including the number of drugs prescribed per patient, how recently the drugs were prescribed and how many different providers wrote prescriptions for each patient.

If a person has a Narx score of 200, that means they have 10 times the risk of unintentionally overdosing from prescription drugs as a person with a score of 0.

Typically, about 75% of patients in the state score below a 200 on any given day, but the researchers found that 32 percent of the U-M patients were above that threshold.

The U-M team then looked at data from the Michigan Bariatric Surgery Collaborative, a statewide initiative that aims to improve the quality of bariatric surgery, to determine the number of refills and emergency room visits within a month of each patient's weight-loss procedure.

Eighty-three percent of patients with a Narx score over 200 received more than 10 pills of an opioid that was not the same as the one prescribed to help them cope with pain as they recovered from their surgeries — compared to zero patients with a Narx score under 100.

In more than two-thirds of these instances, the health care providers who wrote these additional prescriptions were not part of the bariatric surgery program at U-M Health.

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In addition, no patients with a Narx score under 100 had what's known as a preventable emergency room visit — when someone visits the emergency room for a health concern that is not severe enough to require hospitalization nor related to a complication from surgery — while 8% of patients with a score of 200 and above did.

"Our goal and focus is still to limit the amount of opioids prescribed," Varban said. "The one thing that we would probably change based on these results is to do more follow-up amongst patients with a higher Narx score to establish better non-narcotic pain control options and to help patients avoid unnecessary emergency room visits."

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This research used data from the Michigan Bariatric Surgery Collaborative, a quality collaborative initiative funded by Blue Cross Blue Shield.

Paper cited: "Patient characteristics and outcomes among bariatric surgery patients with high narcotic overdose scores," Surgical Endoscopy. DOI: 10.1007/s00464-022-09205-x