Overview
Tirzepatide is a once-weekly injectable peptide that acts as a dual agonist of the glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors. It was developed by Eli Lilly and received FDA approval for type 2 diabetes (Mounjaro) in 2022 and for chronic weight management (Zepbound) in 2023.
Mechanism of Action
Tirzepatide works by activating both GIP and GLP-1 receptors simultaneously:
- GLP-1 receptor activation: Enhances glucose-dependent insulin secretion, suppresses glucagon, slows gastric emptying, and reduces appetite
- GIP receptor activation: Potentiates insulin secretion, may enhance fat metabolism, and appears to reduce nausea compared to GLP-1-only agonists
Research and Clinical Trials
The SURMOUNT clinical trial program demonstrated significant weight loss results:
- SURMOUNT-1: Average weight loss of 20.9% with the highest dose over 72 weeks
- SURMOUNT-2: Significant improvements in both weight and glycemic control in patients with type 2 diabetes
Dosing
Tirzepatide is administered via subcutaneous injection once weekly. The dose is typically titrated from 2.5 mg up to a maximum of 15 mg based on tolerability and treatment goals.
Side Effects
Common side effects include:
- Nausea and vomiting
- Diarrhea or constipation
- Abdominal pain
- Decreased appetite
Important Considerations
Tirzepatide is a prescription medication and should only be used under medical supervision. It is not approved for cosmetic weight loss and carries a boxed warning about potential thyroid C-cell tumors based on animal studies.