MHRA Drug Safety Update

The UK Medicines and Healthcare products Regulatory Agency (MHRA) has published a Drug Safety Update warning that non-arteritic anterior ischaemic optic neuropathy (NAION) has been very rarely reported in association with semaglutide (Wegovy, Ozempic, Rybelsus). The update applies across all licensed indications: type 2 diabetes, weight management, and cardiovascular risk reduction.

NAION is a condition caused by reduced blood flow to the optic nerve, typically resulting in sudden, painless vision deterioration — usually in one eye. It is a recognised but uncommon ophthalmological event in the general population, and the MHRA's update signals that semaglutide may very rarely be a contributing factor.

Key Recommendations

The MHRA advises healthcare professionals to:

  • Refer patients urgently for ophthalmological assessment if they report sudden or partial vision loss while taking semaglutide
  • Discontinue semaglutide if NAION is diagnosed
  • Report suspected adverse reactions via the Yellow Card scheme

Patients are advised to seek immediate medical attention if they experience sudden vision changes, including blurring, darkening, or loss of vision in one or both eyes.

EMA PRAC Review

The European Medicines Agency's Pharmacovigilance Risk Assessment Committee (PRAC) discussed semaglutide and NAION as a safety signal at its meeting on 7–10 April 2025. The signal was initiated following case reports in the EudraVigilance database. The PRAC's review is part of the standard EU pharmacovigilance process for evaluating emerging safety data.

Context: The NAION Signal

The potential link between GLP-1 receptor agonists and NAION first drew attention following a 2024 retrospective cohort study published in JAMA Ophthalmology, which suggested an increased relative risk of NAION in patients prescribed semaglutide. The study, by Hathaway et al., examined over 17,000 patients and identified a higher incidence of NAION among semaglutide users compared to those on other medications.

However, the absolute risk remains very low. NAION is itself rare, with an estimated annual incidence of 2.3–10.2 per 100,000 in the general population over age 50. The MHRA emphasises that the association has been "very rarely reported."

Broader GLP-1 Safety Landscape

This NAION signal is the latest in a series of safety evaluations for GLP-1 receptor agonists. In 2024, the FDA declined to add a boxed warning for suicidal ideation after a review found insufficient evidence of a causal link. Other signals under monitoring include pancreatitis, gallbladder events, and gastrointestinal adverse effects.

For the research community, the MHRA update underscores the importance of ongoing pharmacovigilance for peptide therapeutics, particularly as GLP-1 agonist use continues to expand rapidly across obesity and metabolic disease indications.

What This Means for Peptide Researchers

This safety signal is specific to pharmaceutical-grade semaglutide products licensed for human use. Research-grade semaglutide sold for laboratory research is not subject to the same pharmacovigilance framework, but researchers should be aware of the evolving safety profile. The MHRA's action does not affect the legal status of research peptides, but it reinforces the regulatory distinction between licensed medicines and unlicensed research compounds.

Researchers working with GLP-1 receptor agonists should monitor EMA and MHRA updates as the PRAC review progresses, and incorporate emerging safety data into their research protocols and risk assessments.

This article is for research and educational purposes only and does not constitute medical advice. Semaglutide (Wegovy, Ozempic, Rybelsus) is a prescription-only medicine in the UK. Research-grade peptides are not licensed medicines and are intended for laboratory research purposes only.

This article is AI-researched and editorially reviewed. It is provided for research and educational purposes only and is not medical advice. Research peptides are not licensed for human consumption in the UK.