Zepbound vs. Mounjaro: What's the difference?

On November 8, 2023 the FDA approved Lilly’s Zepbound (tirzepatide) for chronic weight management. This treatment stands out as the first and only approved therapy that activates two incretin hormone receptors, GIP and GLP-1, addressing an underlying cause of excess weight.

Lilly has another tirzepatide drug agent in its portfolio known as Mounjaro, primarily prescribed for managing Type 2 Diabetes. While both Zepbound and Mounjaro share the same injectable form and mechanism of action, the key difference lies in their indications.

To simplify, if a person has type 2 diabetes, their doctor may prescribe Mounjaro. If someone is overweight or obese and has at least one weight-related condition, their doctor may prescribe Zepbound. Here is a table summarizing the key characteristics for Zepbound and Mounjaro:

	Zepbound	Mounjaro
Manufacturer	Eli Lilly	Eli Lilly
Generic Name	​Tirzepatide	​​Tirzepatide
Age Limit	18 years or older	​18 years or older
How does this drug work?	​Glucose-dependent insulinotropic polypeptide (GIP) receptor and glucagon-like peptide-1 (GLP-1) receptor agonist	​Glucose-dependent insulinotropic polypeptide (GIP) receptor and glucagon-like peptide-1 (GLP-1) receptor agonist
Indication	​Adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in adults with an initial body mass index (BMI) of: 30 kg/m2 or greater (obesity) or 27 kg/m2 or greater (overweight) in the presence of at least one weight-related comorbid condition*	Adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus.
Dosage Forms	Prefilled single-use injection pen delivering doses of either 2.5mg/0.5mL, 5mg/0.5mL, 7.5mg/0.5mL, 10mg/0.5mL, 12.5mg/0.5mL, or 15mg/0.5mL	Prefilled single-use injection pen delivering doses of either 2.5mg/0.5mL, 5mg/0.5mL, 7.5mg/0.5mL, 10mg/0.5mL, 12.5mg/0.5mL, or 15mg/0.5mL
Administration	​​Inject subcutaneously once weekly on the same day, at any time, with or without food (rotate injection site with each injection). Start at 2.5 mg, increase every 4 weeks up to 15mg.	​Inject subcutaneously once weekly on the same day, at any time, with or without food (rotate injection site with each injection). Start at 2.5 mg, increase every 4 weeks up to 15mg.
Side Effects	​Common side effects (occurred in at least 5% of patients): Stomach/GI discomfort Nausea/Vomiting Diarrhea Injection site reactions Fatigue Hypersensitivity reactions Hair loss	​Common side effects (occurred in at least 10% of patients): Stomach/GI discomfort Nausea Diarrhea Decreased appetite
Warnings	​Serious warnings: Risk of thyroid C-cell tumors, Multiple Endocrine Neoplasm Syndrome Type 2 (MEN 2) Acute pancreatitis Low glucose levels with concomitant use of insulin secretagogues or insulin Hypersensitivity reactions Acute kidney injury Severe gastrointestinal disease Diabetic retinopathy complications Acute gallbladder disease Fetal harm (caution if breastfeeding) Suicidal behavior and ideation	​Serious warnings: Risk of thyroid C-cell tumors, Multiple Endocrine Neoplasm Syndrome Type 2 (MEN 2) Acute pancreatitis Low glucose levels with concomitant use of insulin secretagogues or insulin Hypersensitivity reactions Acute kidney injury Severe gastrointestinal disease Diabetic retinopathy complications Acute gallbladder disease Heart rate increase Fetal harm (caution if breastfeeding)
Ingredients	​Active medicinal ingredient: Tirzepatide Inactive agents: sodium chloride, sodium phosphate dibasic heptahydrate, and water for injection. Hydrochloric acid solution and/or sodium hydroxide solution may have been added to adjust the PH.	​Active medicinal ingredient: Tirzepatide Inactive agents: sodium chloride, sodium phosphate dibasic heptahydrate, and water for injection. Hydrochloric acid solution and/or sodium hydroxide solution may have been added to adjust the PH.
Animal-free	​LIKELY	YES
Certified Animal-Free	NO	NO

*Examples of weight-related comorbid condition: hypertension, dyslipidemia, type 2 diabetes mellitus, obstructive sleep apnea or cardiovascular disease

Zepbound Package Insert

Mounjaro Package Insert

Additionally, it is noteworthy to mention Wegovy, manufactured by Novo Nordisk, is another option in the realm of chronic weight management. When considering the most suitable therapeutic option for your specific health needs, it is imperative to engage in a collaborative dialogue with your healthcare provider. Your doctor will assess your health profile and guide you toward the most appropriate choice.

Co-authored by: Trisha Singh

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