Published: 2026-02-06 01:06
MHRA Highlights Rare NAION Risk with Semaglutide (Wegovy, Ozempic, Rybelsus)
The Medicines and Healthcare products Regulatory Agency (MHRA) has issued a drug safety update alerting healthcare professionals to a rare but serious risk of Non-arteritic Anterior Ischemic Optic Neuropathy (NAION) associated with semaglutide. This update applies to all formulations of semaglutide, including Wegovy, Ozempic, and Rybelsus.
While NAION is a known condition with various risk factors, the MHRA’s communication underscores the importance of clinician awareness regarding its potential link to semaglutide use. Healthcare professionals are advised to counsel patients on the symptoms of NAION and to consider the risk in their prescribing decisions, particularly for individuals with pre-existing vulnerabilities.
Understanding Semaglutide and its Indications
Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist, a class of medicines that mimics the effects of natural GLP-1 hormone. It plays a crucial role in glucose-dependent insulin secretion, slows gastric emptying, and promotes satiety. These actions contribute to its efficacy in managing blood glucose levels and facilitating weight loss.
In the UK, semaglutide is licensed under different brand names for specific indications. Ozempic (injectable) and Rybelsus (oral) are approved for the treatment of adults with insufficiently controlled type 2 diabetes mellitus, as an adjunct to diet and exercise. Wegovy (injectable) is indicated for weight management, including weight loss and weight maintenance, in adults with obesity or overweight with at least one weight-related comorbidity. Its widespread use across these conditions means a broad patient population may be exposed to the medicine.
What is Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION)?
NAION is a sudden, painless loss of vision resulting from impaired blood flow to the optic nerve head. It is the most common cause of acute optic neuropathy in individuals over 50 years of age. The condition typically affects one eye, though sequential involvement of the other eye can occur in a significant proportion of patients.
The visual loss can range from mild to severe, often presenting as an altitudinal visual field defect, meaning a loss of vision in the upper or lower half of the visual field. While the exact cause is often multifactorial, NAION is strongly associated with systemic vascular risk factors. These include hypertension, diabetes mellitus, hyperlipidaemia, sleep apnoea, and a small optic disc cup-to-disc ratio (a ‘disc at risk’). Although NAION can lead to permanent vision impairment, some degree of spontaneous recovery may occur in a minority of cases.
The MHRA’s Drug Safety Update
The MHRA’s alert stems from a review of reported cases of NAION in patients using semaglutide. While the overall incidence appears to be rare, the regulatory body has determined that there is a sufficient signal to warrant an update to product information and to inform healthcare professionals. This action ensures that prescribers and patients are fully aware of all potential adverse effects, however infrequent.
The product information for all semaglutide-containing medicines will be updated to include NAION as a potential adverse reaction. This inclusion reflects the MHRA’s commitment to continuously monitoring the safety profile of medicines and communicating relevant findings to the clinical community. It is important to reiterate that “rare” typically signifies an adverse event occurring in between 1 in 1,000 and 1 in 10,000 patients.
Clinical Implications for Prescribers
For clinicians prescribing semaglutide, the MHRA’s update necessitates a review of current practice regarding patient counselling and monitoring.
Patient Counselling
* Inform patients: Discuss the rare risk of NAION with patients initiating semaglutide, particularly those with pre-existing risk factors for the condition.
* Symptoms to watch for: Advise patients to be vigilant for any sudden changes in vision, such as:
* Sudden, painless blurring or loss of vision in one eye.
* A partial loss of vision, often described as a shadow or curtain over part of the visual field.
* Any other unexplained visual disturbances.
* Immediate action: Instruct patients to seek urgent medical attention if they experience any of these symptoms.
Management Upon Symptom Onset
* Discontinue semaglutide: If a patient reports symptoms suggestive of NAION, semaglutide should be discontinued immediately.
* Urgent referral: An urgent ophthalmological assessment is crucial to confirm the diagnosis and manage the condition appropriately. Early diagnosis and intervention can be vital for visual prognosis.
Consideration in High-Risk Patients
When considering semaglutide for patients with multiple pre-existing risk factors for NAION (e.g., uncontrolled hypertension, severe diabetes, sleep apnoea, or a history of NAION in the contralateral eye), clinicians should carefully weigh the benefits against this rare but serious risk. A thorough discussion with the patient about these considerations is essential for shared decision-making.
Balancing Benefits and Risks
Semaglutide has demonstrated significant clinical benefits in improving glycaemic control in type 2 diabetes and achieving substantial weight loss in individuals with obesity or overweight. These benefits contribute to reducing the risk of serious long-term complications associated with these conditions, such as cardiovascular disease.
The MHRA’s update does not alter the overall positive benefit-risk profile of semaglutide for the majority of patients within its approved indications. Instead, it serves as an important reminder for clinicians to maintain vigilance for all potential adverse effects, even those that are rare. The key is informed prescribing, thorough patient education, and prompt action if adverse reactions occur.
Reporting Suspected Adverse Reactions
Healthcare professionals are strongly encouraged to report any suspected adverse reactions to medicines via the Yellow Card scheme. This includes any cases of NAION or other visual disturbances observed in patients taking semaglutide. Reporting helps the MHRA to continuously monitor the safety of medicines in the UK and to take necessary action to protect public health.
Reports can be submitted online at www.gov.uk/yellowcard, or by searching for ‘MHRA Yellow Card’ in the Google Play or Apple App Store.
Source: Gov UK
