Are Zepbound and Mounjaro the Same Drug?
No, Zepbound and Mounjaro are not the same. Both contain the active ingredient tirzepatide, a dual GLP-1 and GIP receptor agonist developed by Eli Lilly.[1] They differ in FDA-approved uses, branding, and dosing details.
What Are They Approved For?
Mounjaro treats type 2 diabetes in adults, helping control blood sugar alongside diet and exercise.[1] Zepbound treats moderate to severe obesity in adults with at least one weight-related condition (like high blood pressure or high cholesterol), or in those with BMI ≥30, combined with reduced-calorie diet and exercise.[1] Neither is approved for type 1 diabetes.
How Do They Differ in Practice?
| Aspect | Mounjaro | Zepbound |
|--------|----------|----------|
| Primary Indication | Type 2 diabetes | Weight management/obesity |
| Available Strengths | 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, 15mg | 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, 15mg |
| Dosing Schedule | Weekly subcutaneous injection | Weekly subcutaneous injection |
| Boxed Warning | Thyroid C-cell tumor risk (same for both) | Thyroid C-cell tumor risk (same for both) |
The pens look identical and deliver the same doses, leading some patients to confuse them or use one off-label for the other's purpose.[2]
Can You Switch Between Them?
Patients sometimes get pharmacy substitutions due to shortages, but doctors advise against it without guidance. Mounjaro's diabetes approval doesn't cover obesity as primary use, and Zepbound lacks diabetes approval. Insurance coverage varies—Mounjaro often covers diabetes better, Zepbound for weight loss.[2]
Common Side Effects and Risks
Both share risks like nausea, diarrhea, vomiting, constipation, abdominal pain, injection site reactions, fatigue, hypersensitivity, and hypoglycemia (with insulin or sulfonylureas).[1] Zepbound trials showed 16-21% average weight loss over 72 weeks; Mounjaro diabetes trials showed 5-10kg loss as a secondary benefit.[1]
Who Makes Them and Availability?
Eli Lilly manufactures both. Mounjaro launched in 2022; Zepbound in late 2023. Ongoing shortages affect access, with compounded versions available from pharmacies but lacking FDA approval.[2]
Patent and Exclusivity Timeline
Tirzepatide patents extend to 2035-2036, per DrugPatentWatch.[3] No generics or biosimilars yet; Eli Lilly faces challenges but holds strong exclusivity.
[1]: FDA Labels - https://www.accessdata.fda.gov/drugsatfdadocs/label/2023/215866s000lbl.pdf (Mounjaro), https://www.accessdata.fda.gov/drugsatfdadocs/label/2023/217806s000lbl.pdf (Zepbound)
[2]: Eli Lilly - https://www.lilly.com/news/media/media-kits/zepbound
[3]: DrugPatentWatch.com - https://www.drugpatentwatch.com/p/tradename/ZEPBOUND