A dual GIP/GLP-1 receptor agonist with the highest weight loss efficacy of any approved medication.
Tirzepatide is a first-in-class dual agonist that simultaneously activates both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors. Developed by Eli Lilly, it represents a novel mechanism beyond existing GLP-1-only drugs. GIP amplifies the metabolic effects of GLP-1 and may reduce some GI side effects while enhancing fat-burning in adipose tissue.
The drug was first approved by the FDA in May 2022 as Mounjaro for type 2 diabetes management. It received FDA approval in November 2023 as Zepbound for chronic weight management in adults with obesity or overweight with weight-related conditions. This makes tirzepatide one of the most rapidly developed and approved obesity medicines in history.
Like semaglutide, tirzepatide became a target for compounding during branded product shortages. The FDA placed tirzepatide on its drug shortage list and later updated shortage status. Compounding is permissible only during FDA-declared shortage periods. Patients should verify the regulatory status of any tirzepatide they are prescribed.
The SURMOUNT clinical trial program produced landmark results. SURMOUNT-1 showed 20.9% average body weight reduction at 72 weeks with the 15 mg dose — the highest ever recorded for a pharmacological weight loss treatment. SURMOUNT-2 demonstrated similarly impressive results in patients with type 2 diabetes.
The SURPASS trial program established tirzepatide's diabetes efficacy, showing HbA1c reductions superior to semaglutide in head-to-head comparison (SURPASS-2). Cardiovascular outcomes trial (SURMOUNT-MMO) data is anticipated. The mechanism of dual GIP/GLP-1 agonism appears to provide additive or synergistic metabolic benefits.
📚 Key Reference: PMID: 35366306 (SURMOUNT-1), PMID: 34536961 (SURPASS-2)
Side effect profile is similar to GLP-1 agonists: nausea, diarrhea, vomiting, constipation, decreased appetite. Generally better-tolerated than some older GLP-1 agents, possibly due to GIP activity. Same precautions apply: history of medullary thyroid carcinoma or MEN-2 syndrome contraindicates use. Pancreatitis and gallbladder disease risks exist. Patients with diabetic retinopathy should be monitored. Always consult your provider.
Tirzepatide is FDA-approved as Mounjaro (Eli Lilly, diabetes indication, May 2022) and Zepbound (Eli Lilly, weight management, November 2023). Compounded versions were permitted during FDA-declared shortage periods. FDA shortage status has been updated and patients should verify current compounding legality with their provider.