Patients taking the commonly prescribed diabetes and weight loss drugs Ozempic and Wegovy were at greater risk of optic nerve stroke, which can lead to blindness, according to a new study from researchers at Mass General Brigham.
The study said people prescribed semaglutide, sold under the brand names Ozempic for diabetes or Wegovy for weight loss, were more likely to be diagnosed with NAION than people with diabetes or obesity who didn’t take the drugs. Researchers cautioned that they have no evidence that semaglutide causes this potentially blinding condition, only that the study showed that patients taking the diabetes or weight loss medications were at 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 the rare condition. However, he said there is not enough evidence to show that semaglutide causes NAION.
“I would consider it serious, cautionary information — the kind of information that physicians should be using in conversations with their patients,” said Rizzo, the study’s author and a professor of ophthalmology at Harvard Medical School.
He added that patients should consider the study findings when deciding whether to start the drugs.
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 do not show a “causal association” between the drugs and the condition. The company added that NAION is not listed as a possible side effect in the marketing labels of the drugs approved by the Food and Drug Administration.
“Semaglutide has been studied in large-scale real-world experience studies and robust clinical development programs with cumulative exposure of more than 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 affects 2 to 10 out of every 100,000 people. Like a stroke, it is caused by reduced blood flow to the optic nerve, which can damage tissue. It is the second most common cause of blindness from optic nerve damage, after glaucoma. People with high blood pressure or diabetes are also at increased risk for NAION.
Last summer, doctors at Mass Eye and Ear noticed that 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 researchers to dig deeper.
Researchers analyzed data from about 17,000 Mass Eye and Ear patients over six years, limiting the data to those who had type 2 diabetes or obesity. The six-year period matched the time when Ozempic was on the market. The researchers compared patients who were prescribed semaglutide with those who took other diabetes or weight loss medications.
Rizzo said there is no diagnostic code for NAION, so researchers narrowed down the cases by looking for a related term, ischemic optic neuropathy. From there, they confirmed the cases by reviewing medical records.
What did the research yield?
Of the 710 people with diabetes, 194 were prescribed semaglutide, while 516 were taking other medications. However, 17 patients taking semaglutide had NAION, while only six patients taking 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 prescribed semaglutide, 20 developed NAION. Of the 618 obese or overweight patients taking 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 cause and effect.”
He said that further research into possible cause and effect would require a much larger group of patients.
The study drew patients from a single medical practice in the Boston area, which sees a substantial portion of the region’s NAION patients, so the study authors noted that the findings may not translate to the general population. Researchers also didn’t know whether patients prescribed semaglutide actually took the medication, or whether they started and stopped taking it. However, researchers confirmed that pharmacies filled the prescriptions.
Another recent non-peer-reviewed study found that more than half of people prescribed the 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 percent did not complete a 12-week course of the drugs liraglutide or semaglutide, which are sold under the brand names Saxenda and Wegovy.
Manufacturers of these blockbuster weight-loss and diabetes drugs, which belong to a class of drugs called GLP-1 agonists, or glucagon-like peptide 1, are already facing dozens of lawsuits from consumers who say they had to have their gallbladders removed or suffered a form of stomach paralysis after taking the drug.