Wegovy Weight-Loss Drug Linked to Fivefold Higher Risk of Sudden Vision Loss
Patients using the weight-loss medication Wegovy have nearly five times the risk of sudden sight loss compared to those taking the diabetes drug Ozempic, according to a large-scale study published in the British Journal of Ophthalmology. The research highlights a significant association between Wegovy and non-arteritic anterior ischemic optic neuropathy (Naion), commonly referred to as 'eye strokes,' which cause sudden and often permanent vision impairment due to reduced blood flow to the optic nerve.
Study Details and Findings
The study examined adverse event reports submitted to the US Food and Drug Administration between December 2017 and December 2024. Canadian researchers compared incidents of Naion linked to various semaglutide-based drugs, including up to 2mg of weekly injectable Ozempic for type 2 diabetes, up to 2.4mg of weekly injectable Wegovy for obesity, and daily Rybelsus tablets for type 2 diabetes, as well as tirzepatide (sold as Mounjaro).
Results indicated that Wegovy had the strongest association with sudden vision loss, with a fivefold greater chance of developing Naion compared to Ozempic. Men were found to have three times the risk of women. In contrast, no increased risk was detected with Rybelsus tablets or tirzepatide. The authors suggested that the high doses and faster-acting nature of Wegovy injections might explain the heightened association, whereas the limited absorption and slower uptake of Rybelsus likely account for the absence of a detectable link.
Expert Insights and Regulatory Warnings
Dr. Edward Margolin, from the University of Toronto's department of ophthalmology and a co-author of the study, stated that Naion is likely a genuine side-effect of semaglutide. He noted that more aggressive or rapid weight loss could potentially increase the risk of this condition. Although rare, affecting approximately one in 10,000 semaglutide users, the study identified a potential dose-dependent safety concern.
In February, the UK Medicines and Healthcare products Regulatory Agency issued a drug safety update warning about the risk of Naion, following similar alerts from European regulators. Dr. Alison Cave, the MHRA's chief safety officer, emphasized that while the risk is extremely low, patients and prescribers must be aware of symptoms to ensure prompt treatment if side-effects occur.
Industry Response and Further Research
A spokesperson for Novo Nordisk, the manufacturer of Wegovy, Ozempic, and Rybelsus, affirmed that patient safety is a top priority and that the company monitors adverse events closely. They added that EU patient leaflets have been updated to include Naion but maintained that evidence does not suggest a causal relationship, with the benefit-risk profile of semaglutide remaining favourable.
Samantha Mann, a consultant ophthalmologist at the Royal College of Ophthalmologists, cautioned that the study relies on reported side-effects and cannot prove causation. She noted that an increase in optic nerve strokes has not been widely observed in clinical practice at St Thomas' in London, underscoring the need for further research to clarify the actual risk.
This research adds to ongoing discussions about the safety of GLP-1 receptor agonist medicines, which are praised for benefits like reduced heart attack risks and appetite suppression but now face scrutiny over potential vision-related side-effects.
