Despite their shared purpose as once-weekly injections for Type 2 diabetes, Mounjaro and Trulicity are distinct medications with important differences in their active ingredients, mechanisms of action, approved uses, and overall efficacy. Understanding these variations is crucial for patients and healthcare providers in determining the most suitable course of treatment.
Mounjaro vs. Trulicity: A Tale of Two Incretins
Both Mounjaro and Trulicity belong to a class of drugs that mimic incretin hormones, which are naturally released by the gut in response to eating. These hormones signal the pancreas to release insulin, decrease the amount of sugar produced by the liver, and slow down digestion. However, their mechanisms of action diverge in a fundamental way.
The Dual Action of Mounjaro
Mounjaro's active ingredient is tirzepatide, a first-in-class dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. This 'twincretin' approach means it mimics two distinct natural hormones, leading to significant reductions in HbA1c and greater weight loss.
The Single Action of Trulicity
Trulicity's active ingredient, dulaglutide, is solely a GLP-1 receptor agonist. It mimics the natural GLP-1 hormone to control blood glucose and regulate appetite. While effective, its single-receptor mechanism typically results in less pronounced effects on blood sugar and weight compared to Mounjaro.
FDA-Approved Uses and Eligibility
Mounjaro and Trulicity have different FDA-approved indications. Mounjaro is approved to improve blood sugar in adults with Type 2 diabetes and its active ingredient (tirzepatide) is also approved for chronic weight management under the brand name Zepbound. Trulicity is approved for adults and children (age $\ge$ 10) with Type 2 diabetes for blood sugar control and to reduce the risk of major cardiovascular events in adults with established heart disease or multiple risk factors.
Comparison of Mounjaro vs. Trulicity
| Feature | Mounjaro (Tirzepatide) | Trulicity (Dulaglutide) |
|---|---|---|
| Mechanism of Action | Dual GIP and GLP-1 receptor agonist | Single GLP-1 receptor agonist |
| Efficacy for A1C Reduction | Greater A1C reduction demonstrated in clinical trials | Effective, but generally less potent than Mounjaro for A1C reduction |
| Efficacy for Weight Loss | Leads to significantly greater weight loss due to its dual mechanism | Provides moderate weight loss; less pronounced than Mounjaro |
| FDA-Approved Uses | Type 2 Diabetes (adults only); the active ingredient is also approved for weight management under the brand name Zepbound | Type 2 Diabetes (adults and children $\ge$ 10); also approved for cardiovascular event risk reduction in adults |
| Common Side Effects | Nausea, diarrhea, decreased appetite, vomiting, constipation, stomach pain | Nausea, diarrhea, vomiting, abdominal pain, decreased appetite |
| Administration | Once-weekly subcutaneous injection | Once-weekly subcutaneous injection |
| Dosage Range (Adults) | Starts at 2.5 mg, can go up to 15 mg weekly | Starts at 0.75 mg, can go up to 4.5 mg weekly |
Side Effects and Risks
Both medications share common gastrointestinal side effects such as nausea, diarrhea, and vomiting, especially when starting or increasing the dose. Higher doses of Mounjaro may be associated with a slightly higher incidence of these effects. Both carry a boxed warning about the potential risk of thyroid C-cell tumors based on animal studies and are not recommended for individuals with a history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. Rare serious side effects like pancreatitis and gallbladder issues have also been reported with both.
Conclusion
Mounjaro and Trulicity are distinct once-weekly injectable treatments for Type 2 diabetes. Mounjaro's dual GIP and GLP-1 agonist mechanism offers superior blood sugar control and weight loss compared to Trulicity's single GLP-1 agonist action. Trulicity, however, is approved for cardiovascular risk reduction and use in younger patients. Selecting the appropriate medication requires consultation with a healthcare provider to consider individual health factors, goals, and potential risks and benefits.
