Tirzepatide (Zepbound)

Tirzepatide, marketed as Zepbound for obesity and Mounjaro for type 2 diabetes, is a first-in-class dual agonist that simultaneously activates both GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) receptors. This dual mechanism amplifies satiety signaling beyond what GLP-1 alone can achieve, leading to calorie reduction that outpaces any single-receptor agent. FDA approved for chronic weight management in November 2023, tirzepatide arrived with landmark data from the SURMOUNT-1 trial, where participants at the 15mg dose lost a mean 20.9 percent of body weight versus just 3.1 percent in the placebo group over 72 weeks. When put head-to-head against the previous standard-of-care in SURMOUNT-5, tirzepatide delivered 20.2 percent weight loss compared to semaglutide's 13.7 percent — a 6.5 percentage point separation that is clinically enormous in obesity medicine. A network meta-analysis of all weight-loss interventions gave tirzepatide the highest SUCRA score of 91.2 among GLP-1 class drugs, confirming its statistical dominance. Dosing begins at 2.5mg weekly, titrating over 20 weeks to a target of 10mg or 15mg, administered via a simple auto-injector pen with no food restrictions. Through Lilly Direct, the self-pay price runs $299 to $449 per month — a significant reduction from the $1,023 to $1,349 list price. The 2026 formulary changes affected millions of commercially insured patients when CVS Caremark dropped Zepbound, but Medicare's Bridge program starting July 1, 2026 reopens coverage at roughly $50 per month for 3.4 million beneficiaries. Ideal patients include those with obesity BMI ≥30, or ≥27 with a comorbidity, who have not responded adequately to lifestyle intervention and prefer maximum efficacy as the primary goal.