The South Korean Ministry of Food and Drug Safety (KFDA) has issued a warning regarding GLP-1 weight loss medications, including Wegovy and Mounjaro, advising patients to discontinue use and seek immediate medical attention if they experience sudden vision loss in one eye.
On November 11, the KFDA distributed a 'drug safety letter' recommending that patients stop taking GLP-1 medications if they suspect non-arteritic anterior ischemic optic neuropathy (NAION), a condition that can lead to sudden vision loss due to reduced blood flow to the optic nerve.
The warning applies to medications such as tirzepatide (Mounjaro), semaglutide (Wegovy), liraglutide (Saxenda), and efpeglenatide (Epe). The KFDA urged patients to report any symptoms, such as painless vision loss in one eye, to healthcare providers immediately. The agency also requested pharmaceutical companies to submit plans for updating product approvals. The letter clarifies that this does not imply that all products carry the same risk or that patients should stop taking their medications without consulting a doctor.
On November 9, the U.S. Food and Drug Administration (FDA) mandated the inclusion of NAION risk in the warnings and precautions for all approved GLP-1 medications in the United States. A meta-analysis of 126 clinical trials indicated that the incidence of NAION was higher in the GLP-1 treatment group, with 6.4 cases per 100,000 person-years compared to 3.8 cases in the control group. The FDA noted that while the condition is rare, the mechanism of its association with these drugs has not been confirmed. The European Medicines Agency (EMA) classified NAION as a 'very rare' adverse reaction (up to 1 in 10,000) for semaglutide products in June 2025.
In South Korea, relevant statistics were revealed during a recent parliamentary audit. KFDA Commissioner Oh Yu-kyung reported that one case of suspected NAION was received following GLP-1 treatment in December 2024, describing the side effect as 'rare but possible.' However, data obtained by Democratic Party lawmaker Nam In-soon from the Health Insurance Review and Assessment Service indicated that 104 patients (67 from Wegovy and 37 from Mounjaro) received treatment for NAION between October 2024 and August 2026. The number of treated patients reflects medical histories following prescriptions and does not confirm a causal relationship with the medications.
The KFDA updated the approval information for Wegovy to include NAION as a new adverse event on October 7.
* This article has been translated by AI.
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