Dozens of people in the United States have filed lawsuits against pharmaceutical companies that make popular GLP-1 medicines, alleging that the drugs caused a...
Dozens of people in the United States have filed lawsuits against pharmaceutical companies that make popular GLP-1 medicines, alleging that the drugs caused a rare eye condition that can result in permanent vision loss.
The lawsuits involve medicines including Ozempic, Wegovy, Mounjaro and Zepbound, which are widely used to treat type 2 diabetes and, in some cases, obesity and chronic weight management.
The legal claims centre on a condition known as nonarteritic anterior ischemic optic neuropathy, commonly referred to as NAION.
NAION occurs when blood flow to the optic nerve is disrupted, potentially causing sudden vision loss. The condition is generally painless and can result in permanent impairment.
Recent US reporting has highlighted dozens of lawsuits alleging that manufacturers failed to adequately warn patients about a possible association between GLP-1 medicines and NAION. However, medical researchers have not established that the drugs cause the condition, and evidence concerning the possible connection remains mixed.
The litigation has brought additional scrutiny to an industry that has experienced rapid growth as GLP-1 medicines have become increasingly popular among patients seeking treatment for diabetes and obesity.
Novo Nordisk, the manufacturer of Ozempic and Wegovy, has rejected the claims and said it considers the personal injury lawsuits to be without merit.
Eli Lilly, which manufactures Mounjaro and Zepbound, has also been involved in the litigation. The companies face allegations that their products can increase the risk of NAION and that patients were not adequately warned about the potential risk.
A federal judicial panel consolidated related NAION lawsuits involving Novo Nordisk and Eli Lilly in the US District Court for the Eastern District of Pennsylvania for coordinated pretrial proceedings.
Court documents show that the cases include allegations involving the development, manufacture, testing, regulatory history, promotion and labelling of the medicines, as well as claims that the products caused NAION. Plaintiffs have brought claims including failure to warn, design defect and breach of warranties.
What is NAION?
NAION is a form of sudden optic nerve damage caused by insufficient blood flow to the optic nerve.
It is sometimes described as an “eye stroke” because of the way the interruption of blood supply can damage the optic nerve.
People who develop NAION can experience sudden vision changes, usually without pain. The resulting damage can be permanent, although the extent of vision loss can vary.
The possible relationship between GLP-1 medicines and NAION has been the subject of scientific research in recent years.
Some studies have reported an association between semaglutide and NAION, while other research has not established a connection.
The American Academy of Ophthalmology has noted that the association remains controversial and that patients should not stop taking semaglutide solely because of the findings from observational research. (EyeWiki)
What does the research show?
The evidence has not produced a single conclusion about whether GLP-1 medicines cause NAION.
The European Medicines Agency’s safety committee reviewed available evidence concerning semaglutide, the active ingredient in Ozempic and Wegovy.
In June 2025, the EMA concluded that NAION should be classified as a very rare side effect of semaglutide medicines, meaning it may affect up to one in 10,000 people taking the medicine.
The agency said several large epidemiological studies suggested that adults with type 2 diabetes taking semaglutide had approximately twice the risk of developing NAION compared with people who were not taking the medicine. It estimated this represented about one additional case per 10,000 person-years of treatment.
The EMA recommended updating product information for semaglutide medicines to include NAION as a very rare side effect.
It also advised patients who experience sudden loss of vision or rapidly worsening eyesight while taking semaglutide to contact a doctor without delay.
However, this finding relates specifically to semaglutide and does not establish that every GLP-1 medicine carries the same level of risk.
What does the US FDA say?
The US Food and Drug Administration has also been examining the possible association.
FDA safety-monitoring information lists NAION among the potential safety signals being evaluated for several GLP-1 medicines, including Mounjaro, Ozempic, Wegovy and Zepbound. The agency has said it is evaluating whether regulatory action is necessary.
The FDA’s investigation means the US regulatory position remains an important part of the developing issue.
The agency has not established through that evaluation that GLP-1 medicines cause NAION.
That distinction is important because an adverse-event signal or lawsuit allegation does not by itself establish that a medicine caused an injury.
What are the lawsuits claiming?
The lawsuits generally allege that patients developed NAION after using GLP-1 medicines and that manufacturers failed to adequately warn consumers and healthcare professionals about the alleged risk.
Some cases have been filed in federal courts, while other lawsuits have been brought in state courts.
The federal cases were consolidated for coordinated pretrial proceedings in Pennsylvania after the Judicial Panel on Multidistrict Litigation determined that the lawsuits involved common factual questions.
The court said centralisation would promote the efficient handling of the litigation and reduce the possibility of duplicated discovery and inconsistent pretrial proceedings.
Individual claims will still have to be addressed through the legal process.
Drugmakers dispute the allegations
Novo Nordisk has strongly disputed the claims made in the lawsuits.
The company has pointed to research that it says does not establish a causal relationship between its medicines and NAION.
Recent reporting quoted a Novo Nordisk spokesperson as saying the company believes the US personal-injury lawsuits are without merit and that it is vigorously defending them.
The company has also been involved in research examining the possible relationship between its medicines and NAION.
This creates an important divide in the developing debate: some observational studies have identified a possible association, while other research has not found evidence that the medicines themselves cause the condition.
What should patients know?
The current evidence does not mean that people taking GLP-1 medicines will develop NAION.
The EMA classified NAION as a very rare side effect of semaglutide, with an estimated frequency of up to one case per 10,000 people taking the medicine.
Patients who experience sudden vision loss or rapidly worsening eyesight should seek urgent medical attention.
People taking GLP-1 medicines should not stop treatment without discussing it with their doctor, particularly because the medicines may be prescribed for important conditions such as type 2 diabetes and obesity.
The lawsuits and regulatory reviews are continuing as scientists and regulators assess the available evidence.
For now, the central question in the litigation remains whether there is a causal relationship between particular GLP-1 medicines and NAION and, if so, whether manufacturers adequately warned patients about the risk.
That question has not been finally determined by the courts.
