Mounjaro, Zepbound & NAION: What You Need to Know

Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist manufactured by Eli Lilly, approved by the FDA in May 2022 for type 2 diabetes. Zepbound (tirzepatide) is the same drug approved in November 2023 for chronic weight management. Trulicity (dulaglutide), also by Eli Lilly, is an older GLP-1 agonist.

While the landmark Harvard study focused primarily on semaglutide (the active ingredient in Ozempic and Wegovy), Mounjaro and Zepbound are named in MDL 3163 based on the shared GLP-1 receptor agonist mechanism and emerging evidence that the class-wide GLP-1 effect on optic nerve vasculature may extend to tirzepatide.

Tirzepatide difference: Mounjaro and Zepbound are unique because they are dual GIP/GLP-1 agonists — they target both the GLP-1 receptor and the GIP receptor. This dual mechanism makes them even more potent than pure GLP-1 agonists like semaglutide, with potentially broader effects on vascular and autonomic physiology.

Why Are Eli Lilly Drugs in the GLP-1 NAION MDL?

The inclusion of Mounjaro, Zepbound, and Trulicity in MDL 3163 is based on several factors:

  • Shared drug class: All GLP-1 receptor agonists share mechanisms that may affect optic nerve blood supply, regardless of the specific molecule
  • Class-wide theory: Plaintiffs allege that the GLP-1 receptor agonist mechanism itself — not just semaglutide specifically — poses optic nerve vascular risks
  • Failure to investigate: Eli Lilly is alleged to have failed to adequately study or monitor for NAION following the Harvard study's findings about the GLP-1 drug class
  • Market size: Mounjaro and Zepbound had combined US sales exceeding $11 billion in 2024, with millions of patients exposed

Mounjaro vs. Ozempic: Mechanism Differences

Understanding the mechanism helps explain why Mounjaro is included in NAION litigation:

Drug Mechanism GLP-1 Activity
Ozempic/Wegovy (semaglutide) GLP-1 agonist only High
Mounjaro/Zepbound (tirzepatide) Dual GIP + GLP-1 agonist High + GIP activity
Trulicity (dulaglutide) GLP-1 agonist only Moderate-High

Plaintiffs argue that because all of these drugs activate GLP-1 receptors — which are present in the eye and optic nerve — all carry potential NAION risk through the same fundamental pathway.

Eligibility for Mounjaro / Zepbound NAION Lawsuit

To potentially qualify for a Mounjaro or Zepbound NAION claim:

  1. You had a documented prescription for Mounjaro, Zepbound, or Trulicity
  2. You were diagnosed with NAION by an ophthalmologist
  3. Vision loss occurred during or after use of the drug
  4. No prior NAION diagnosis before starting the medication
  5. Filing within your state's statute of limitations

Note: Tirzepatide-specific NAION cases may require additional scientific analysis beyond the existing semaglutide studies. An experienced mass tort attorney can evaluate the strength of your individual claim.

Check Your Eligibility →

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