Are Zepbound and Mounjaro the Same Drug?
Zepbound and Mounjaro both contain tirzepatide, a dual GLP-1/GIP receptor agonist that reduces appetite and slows digestion. Mounjaro is FDA-approved for type 2 diabetes; Zepbound is approved for weight loss in adults with obesity or overweight plus weight-related conditions. They differ mainly in branding, dosing labels, and marketing focus.[1]
How Do Weight Loss Results Compare?
Clinical trials show similar efficacy since they use identical active ingredient and doses (2.5 mg to 15 mg weekly injections).
- SURMOUNT-1 trial (Zepbound branding): Patients lost 15-22.5% body weight over 72 weeks (vs. 2.4% on placebo). Highest dose (15 mg) averaged 22.5% loss.[2]
- SURMOUNT-2 trial: 15-20.9% loss in those with obesity and type 2 diabetes.[2]
- Mounjaro data from diabetes trials (SURPASS): 15-21% loss over 40-72 weeks, comparable to Zepbound's obesity trials.[3]
Real-world use confirms near-identical results, with average losses of 15-25% over a year depending on adherence and starting weight.
What's the Difference in Dosing and Use?
Doses match exactly, but:
- Zepbound starts at 2.5 mg, ramps to 15 mg max for weight loss.
- Mounjaro follows the same for diabetes, often prioritizing blood sugar control.
Many doctors prescribe Mounjaro off-label for weight loss due to supply and insurance. Zepbound pens are identical to Mounjaro's, just relabeled.[1]
| Dose (mg/week) | Zepbound Weight Loss (SURMOUNT-1) | Mounjaro Weight Loss (SURPASS Trials) |
|----------------|-----------------------------------|---------------------------------------|
| 5 | 16% | 15-17% |
| 10 | 21.4% | 19-21% |
| 15 | 22.5% | 21-23% |
Cost and Insurance Coverage Breakdown
Zepbound lists at $1,060/month without insurance; Mounjaro at $1,023. Manufacturer coupons drop both to $25/month for eligible patients (income-based).[4]
- Medicare covers Mounjaro for diabetes but not Zepbound for weight loss (new 2024 rules may expand).
- Private insurance favors Mounjaro off-label; Zepbound coverage is spotty, often requiring prior authorization.
- Shortages affect both, but Mounjaro prioritized for diabetes.
Side Effects and Safety Profile
Identical risks: nausea (25-35%), diarrhea (20-25%), vomiting (10-15%), constipation, and injection-site reactions. Rare serious issues include pancreatitis, gallbladder problems, or thyroid tumors (boxed warning).[1][2]
No head-to-head trials, but rates match across studies. Weight regain occurs after stopping either (up to 2/3 of loss in a year).[5]
Who Makes Them and Supply Issues?
Eli Lilly manufactures both. Patent protection runs through 2036 for tirzepatide, with challenges from competitors like Viking Therapeutics.[6] Ongoing shortages stem from demand; compounded versions fill gaps but carry FDA warnings for safety.
When to Choose One Over the Other?
Pick Mounjaro if you have diabetes or better insurance coverage. Opt for Zepbound for obesity-focused approval and potentially easier weight-loss claims. Results and safety are equivalent—decision hinges on access and cost.
Sources:
[1]: FDA Labels for Zepbound and Mounjaro
[2]: SURMOUNT Trials (NEJM)
[3]: SURPASS Trials (Lancet)
[4]: Eli Lilly Pricing
[5]: Jastreboff et al., JAMA 2024
[6]: DrugPatentWatch.com - Tirzepatide Patents