The Food and Drug Administration has mandated that all GLP-1 drugmakers add warning labels about nonarteritic anterior ischemic optic neuropathy (NAION), a rare eye condition that can cause sudden, permanent vision loss [1]. The condition affects the optic nerve by reducing or blocking blood flow, resulting in acute, painless vision loss in one eye with no known treatment [1]. NAION is the second most common optic nerve disease in the U.S., occurring in up to 10 out of 100,000 people over age 50, according to the American Academy of Ophthalmology [1].
The FDA's warning requirement applies to all currently marketed GLP-1 drugs, including Novo Nordisk's Ozempic and Wegovy, Eli Lilly's Mounjaro and Zepbound, and several older GLP-1 diabetes medications [1]. The agency initiated its investigation following a 2024 study published in JAMA Ophthalmology that found diabetes patients prescribed semaglutide were four times as likely to develop NAION compared to those not prescribed the drug [1]. The FDA reviewed adverse event reports and analyzed data from multiple clinical trials, finding that cases of NAION have been reported for all currently marketed GLP-1 drugs [1]. However, FDA scientists were unable to identify a specific mechanism explaining how the drugs could increase the risk of the eye condition [1].
Risk factors for NAION overlap with conditions commonly seen in GLP-1 users, including Type 2 diabetes, sleep apnea, and hypertension [1]. Both Novo Nordisk and Eli Lilly stated that patient safety is their top priority in response to the FDA's action [1]. The drug labels already carry additional warnings for pancreatitis, gallbladder problems, and kidney injury, as well as a black box warning—the FDA's strongest safety warning—regarding a possible risk of thyroid tumors [1]. The FDA advised that "patients and caregivers should be aware of a potential increased risk of NAION, a rare condition that can result in acute, painless, decreased vision in one eye, including permanent vision loss" with GLP-1 use [1].
CONCLUSION
The FDA's mandatory warning label requirement for all GLP-1 drugs represents a significant regulatory action that could impact patient adoption and prescribing patterns for blockbuster medications from Novo Nordisk and Eli Lilly. While the exact mechanism linking GLP-1 use to NAION remains unclear, the association with a rare but serious condition causing permanent blindness poses material reputational and commercial risks to the GLP-1 market leaders. This development may prompt increased scrutiny of the risk-benefit profile of these widely-used weight loss and diabetes medications.