Ozempic, Wegovy linked to rare condition that can cause blindness, study says

Patients who took the frequently prescribed diabetes and weight-loss drugs Ozempic and Wegovy faced a greater risk of a stroke of the optic nerve, which can lead to blindness, according to a new study by Mass General Brigham researchers.

The study says people prescribed semaglutide, sold under the brands Ozempic for diabetes or Wegovy for weight loss, were more likely to be diagnosed with a rare condition called NAION than those with diabetes or obesity who did not take the medications. Researchers cautioned they have no evidence that semaglutide causes this potentially blinding condition, merely that the study found patients taking the diabetes or weight-loss medication faced a greater risk of developing it.

Dr. Joseph Rizzo, director of neuro-ophthalmology at Mass General Brigham's Mass Eye and Ear, said the study is the first to link these diabetes and weight-loss drugs to this rare condition. However, he said there is not enough evidence to show semaglutide causes NAION.

"I would take it as a serious, cautionary bit of information - the kind of information that should be used by physicians in discussion with their patients," said Rizzo, the study’s author and an ophthalmology professor at Harvard Medical School.

He added that patients should consider the study's findings when deciding whether to begin the medications.

Novo Nordisk, which markets Ozempic and Wegovy, said in a statement that the pharmaceutical company takes patient safety reports seriously. The company said the study data does not establish a "causal association" between the medications and the condition. The company added that NAION has not been described as a potential side effect for the drugs' marketing labels approved by the Food and Drug Administration.

"Semaglutide has been studied in large real world evidence studies and robust clinical development programs with a cumulative exposure over 22 million patient years," the company said in a statement.

What is NAION and how common is it?

Nonarteritic anterior ischemic optic neuropathy, or NAION, is a rare condition that afflicts 2 to 10 out of 100,000 people. Like a brain stroke, the condition occurs from reduced blood flow to the optic nerve, which can damage tissue. It is the second most common cause of blindness from optic nerve damage, trailing only glaucoma. People with high blood pressure or diabetes also have an elevated risk for NAION.

Last summer, doctors at Mass Eye and Ear noticed three patients had been diagnosed with vision loss due to this rare condition in just one week. All three had been taking semaglutide. This anecdotal finding prompted the researchers to dig deeper.

Researchers analyzed the records of about 17,000 Mass Eye and Ear patients over six years and narrowed the records to those who had either type 2 diabetes or obesity. The six-year period matched the timing that Ozempic has been on the market. The researchers compared patients who were prescribed semaglutide to those taking other diabetes or weight loss medications.

Rizzo said there is no diagnostic code for NAION, so researchers narrowed cases by looking for a related term, ischemic optic neuropathy. From there, they confirmed cases by reviewing medical records.

What did the study find?

Of the 710 people with diabetes, 194 had been prescribed semaglutide while 516 took other medications. However, 17 patients on semaglutide had NAION while just six patients who took other medications had the condition. The same was true when analyzing 979 patients who were obese or overweight. Of the 361 overweight or obese patients who were prescribed semaglutide, 20 developed NAION. Among 618 obese or overweight patients who took other medications, only three had NAION.

"This study clearly shows an association between semaglutide and NAION," Rizzo said. "What we don't know is whether it's a cause and effect."

He said further study exploring a potential cause and effect would require a much larger group of patients.

The study drew patients from a single Boston-area medical practice that sees a substantial portion of the region's patients with NAION, so the study's authors noted the findings might not translate to the general population. Also, researchers did not know whether patients who were prescribed semaglutide actually took the medication, or whether they had started and stopped the medication. However, researchers confirmed pharmacies filled the prescriptions.

Another recent non-peer-reviewed study found more than half of people prescribed weight-loss drugs Saxenda and Wegovy over the past decade ended their treatment too early to realize meaningful health benefits. The Blue Cross Blue Shield Association study of nearly 170,000 people between July 2014 and December 2023 found that 58% didn't complete a 12-week course of the medications liraglutide or semaglutide, which are sold under the brand names Saxenda and Wegovy.

Makers of the blockbuster weight loss and diabetes drugs, part of a medication class called GLP-1 agonists, or glucagon-like peptide 1, already face dozens of lawsuits from consumers who said they needed to have their gallbladder removed or suffered a type of stomach paralysis after taking the drug.

This article originally appeared on USA TODAY: Ozempic, Wegovy linked to rare condition that can cause blindness, study says