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A recent comprehensive study has uncovered a significant disparity in the risk of sudden vision loss between users of Wegovy and those taking Ozempic, both of which contain the active ingredient semaglutide. The findings highlight a fivefold increase in the likelihood of developing non-arteritic anterior ischemic optic neuropathy (Naion) in patients using Wegovy for weight loss, raising critical questions about the safety profiles of these widely prescribed medications.
Understanding the Risks of Semaglutide
The study, published in the British Journal of Ophthalmology, analysed reports of side effects associated with semaglutide from the US Food and Drug Administration’s adverse event reporting system between December 2017 and December 2024. It specifically compared the incidence of Naion among patients taking varying doses of Wegovy, Ozempic, and Rybelsus, as well as tirzepatide (Mounjaro).
Researchers found that Wegovy, which is primarily prescribed for obesity, had a notably stronger association with sudden vision loss compared to Ozempic, a medication aimed at managing type 2 diabetes. While the overall risk of Naion remains low—affecting roughly one in 10,000 users of semaglutide—the study indicated that men face a threefold increased risk compared to women when using Wegovy.
Dr Edward Margolin from the University of Toronto, one of the study’s authors, posited that Naion is likely a genuine side effect of semaglutide. He cautioned that rapid weight loss associated with Wegovy could potentially escalate the risk of this condition.
Insights from the Data
The research primarily focused on reports submitted to the FDA, which allowed the team to draw comparisons across the different formulations of semaglutide. The study’s authors suggested that the higher doses of Wegovy and its quicker action, due to injectable formulation, could account for the increased risk of Naion. In contrast, the daily oral administration of Rybelsus appeared to present no significant link to this condition, likely due to its slower absorption rates.
As health authorities, including the UK Medicines and Healthcare products Regulatory Agency (MHRA), have issued warnings regarding Naion, the implications of these findings are becoming increasingly prominent. Dr Alison Cave, chief safety officer at the MHRA, reassured that while the risk is minimal, it is essential for both patients and healthcare providers to remain vigilant for symptoms and ensure timely treatment if necessary.
Clinical Perspectives and Future Research
Despite the alarming findings, experts urge caution in interpreting the study’s results. Consultant ophthalmologist Samantha Mann highlighted that the reliance on reported side effects means the causation cannot be definitively established. In her experience at St Thomas’ Hospital in London, there has not been a noticeable uptick of Naion cases in routine clinical practice, emphasising the need for further investigation into the association.
Novo Nordisk, the manufacturer of Wegovy and Ozempic, expressed commitment to patient safety, noting their ongoing collaboration with regulatory bodies to monitor and assess the safety of their products. While the company has updated patient information leaflets to include potential risks, it maintains that the overall benefit-risk profile of semaglutide remains favourable.
Why it Matters
The implications of this study extend beyond individual patient safety; they underscore the necessity for ongoing vigilance in pharmacovigilance and the need for comprehensive patient education regarding potential side effects. As weight-loss drugs gain popularity, understanding the broader health implications is crucial. This research serves as a vital reminder that while medications can offer significant benefits, they may also carry risks that warrant careful consideration and further study. As the landscape of obesity treatment evolves, ensuring the safety and well-being of patients must remain a top priority for healthcare providers and pharmaceutical companies alike.
