[BizHanKook] As concerns regarding the safety of GLP-1 receptor agonists—including the much-hyped obesity treatments Wegovy and Mounjaro—continue to arise, attention is shifting toward their long-term prescription for diabetes patients. Overseas regulatory agencies, including those in the U.S. and U.K., have strengthened warnings regarding risks of vision loss and pancreatitis. While the pharmaceutical industry argues that diabetes itself is a risk factor for related conditions, regulators are warning of potential additional risks associated with the drugs. The medical community notes that while vigilance is necessary for these rare adverse reactions, the therapeutic benefits outweigh the risks for many diabetes patients.
Ahead of World Diabetes Day on the 14th, the long-term safety of GLP-1 class treatments is in the spotlight. According to the 11th edition of the ‘Diabetes Atlas’ published last year by the International Diabetes Federation (IDF), the global number of diabetes patients aged 20–79 was estimated at approximately 589 million in 2024, accounting for one in nine adults. In South Korea, according to the ‘Diabetes Fact Sheet 2026’ published by the Korean Diabetes Association last October, the number of diabetes patients aged 30 and older for the 2023–2024 period was estimated at approximately 5.65 million.
GLP-1 drugs were originally developed as treatments for type 2 diabetes before expanding into the obesity treatment market. Novo Nordisk’s semaglutide is the active ingredient in both the diabetes drug Ozempic and the obesity drug Wegovy. Eli Lilly’s tirzepatide was also first approved in the U.S. as the diabetes drug Mounjaro before being expanded into the obesity treatment Zepbound. Tirzepatide is a dual agonist that acts on both GLP-1 and GIP receptors.
These drugs demonstrate efficacy in weight loss as well as blood glucose control, and some formulations have been recognized for their benefits in reducing the risk of cardiovascular and kidney disease. However, as warnings regarding rare, severe adverse reactions have recently been strengthened, critics point out the need to examine how these findings might impact diabetes patients who require long-term blood glucose management.
FDA Issues Warning on Risk of ‘Optic Neuropathy’… What Is the Drug’s Impact?
On the 9th, the U.S. Food and Drug Administration (FDA) ordered the addition of a warning regarding the risk of non-arteritic anterior ischemic optic neuropathy (NAION) to the labeling of all GLP-1 class drugs. NAION is a condition caused by reduced blood flow to the front of the optic nerve, which can lead to sudden, painless vision impairment and potentially permanent vision loss.
In addition, analyses comparing these drugs to other glucose-lowering agents in type 2 diabetes patients have shown signals of an increased risk in some cases.
Following this, the European Medicines Agency (EMA) had already classified NAION as a very rare side effect of semaglutide in June of last year. A large-scale epidemiological study reviewed by the EMA showed that the risk of NAION in type 2 diabetes patients using semaglutide was approximately twice as high as in non-users.
Novo Nordisk emphasized that diabetes and obesity themselves are conditions that affect multiple organs, including the optic nerve. Their stance is that the occurrence of a related disease after drug administration should not immediately be attributed to the drug itself.
A Novo Nordisk official explained, "Some medical professionals argue that we need to examine whether these are drug-induced adverse reactions or if the incidence rate is higher simply because the patient population is already predisposed to these conditions," adding that the risks of the underlying disease itself must be considered.
They added that while there are various interpretations regarding the causal relationship between the drugs and adverse reactions, the company is including warnings in usage guidelines because these are potential rare side effects. They stressed that the FDA’s recent action is intended to disclose the possibility of such adverse reactions occurring with GLP-1 drugs, not to imply that taking the medication will lead to vision loss.
Pancreatitis Warnings Strengthened… Domestic Pharmaceutical Industry Monitors KFDA Response
Pancreatitis has been a known adverse reaction since GLP-1 drugs were first used for diabetes. In January, the U.K.’s Medicines and Healthcare products Regulatory Agency (MHRA) strengthened its warning regarding the risk of severe acute pancreatitis associated with GLP-1 receptor agonists and GIP/GLP-1 dual agonists. This follows reports of rare cases that led to necrotizing pancreatitis or death.
The pharmaceutical industry suggests that the expansion of the obesity treatment market may have heightened interest in these rare adverse events.
A pharmaceutical industry official stated, "As the number of patients taking these medications surges, a very small number of side effects may appear," adding, "It seems the issue of side effects is being highlighted more because obesity treatments are receiving so much attention."
Safety measures for GLP-1 drugs are also underway in South Korea. On the 11th, the Ministry of Food and Drug Safety (KFDA) distributed a letter regarding drug safety concerning the risk of NAION, advising that if symptoms are suspected, patients should stop taking the drug and seek immediate medical attention.
The KFDA has requested that pharmaceutical companies supplying GLP-1 drugs in Korea submit data regarding overseas safety information and plans for changing authorization details. Once the submitted data is reviewed, the ministry will determine whether to update the precautions for use.
A KFDA official explained, "We have distributed letters to patients and medical staff stating that the KFDA is reviewing the issue, and we have requested industry opinions and data," adding, "Since any changes must align with guidelines, we will likely have to wait and see."
Medical Community: “For Some Diabetes Patients, Therapeutic Benefits Outweigh Risks”
The medical community does not believe the recent warnings from overseas regulators mean that long-term use of GLP-1 drugs should be uniformly discontinued. They suggest that the decision to prescribe should be made by comprehensively considering the patient’s comorbidities and therapeutic efficacy.
Ryu Young-sang, a professor of endocrinology at Chosun University, said, "Rare adverse reactions like NAION or pancreatitis should be considered when prescribing," but added, "For type 2 diabetes patients with obesity, especially those at high risk for cardiovascular disease, these drugs offer the advantage of not only improving blood sugar and weight loss but also proven cardiovascular protection, potentially reducing the risk of myocardial infarction or stroke."
He further elaborated, "In such patients, the therapeutic benefit is generally considered to be much greater than the risk. It is reasonable to continue treatment while explaining potential adverse reactions and warning signs to the patient, and monitoring their progress."
For diabetes patients, not only is the risk of rare drug-related adverse events a concern, but so is the risk of complications resulting from failed blood glucose control. In particular, GLP-1 class drugs with proven cardiovascular benefits can be an important treatment option for patients who have cardiovascular disease or are at high risk.
However, how the risk of NAION or pancreatitis changes with long-term administration, and which patient groups are at higher risk, remain tasks that require further investigation. Given the variety of GLP-1 class drugs and the diverse underlying conditions of patients, it is difficult to apply a universal risk level to all medications and patients.
Professor Ryu emphasized, "Rare adverse reactions like NAION or pancreatitis can only be more accurately identified through long-term follow-up of a large number of patients in actual clinical practice. It is necessary to verify the risk by drug type and identify which patients are at greater risk compared to those using other glucose-lowering agents."
He added, "In clinical settings, it is important to have a system that instructs patients to seek immediate care if sudden vision loss or persistent severe abdominal pain occurs, and to promptly evaluate and report suspected cases."