Tirzepatide

Tirzepatide is FDA-approved for three indications: type 2 diabetes (as Mounjaro, approved 2022), chronic weight management in adults with obesity or overweight with a weight-related comorbidity (as Zepbound, approved 2023), and moderate-to-severe obstructive sleep apnea in adults with obesity (as Zepbound, added December 2024). It is the first medication ever approved for pharmacologic treatment of OSA.

In the SURMOUNT-1 trial, adults without diabetes on the 15 mg dose lost an average of 20.9% of body weight at 72 weeks, compared with 3.1% on placebo. About one-third achieved ≥25% weight loss. At the 10 mg dose the mean was 19.5%, and at 5 mg it was 15.0%. Weight loss plateaus around 60–72 weeks and is maintained with continued treatment; discontinuation typically leads to substantial regain.

Same active molecule (tirzepatide), same vial, same dosing range — different FDA indications and insurance coverage. Mounjaro is approved only for type 2 diabetes; Zepbound is approved for chronic weight management and OSA. Your prescriber's choice of brand depends on your indication, because insurance typically only covers the brand matching your diagnosis. Clinically, the drugs are interchangeable.

For weight loss, tirzepatide is superior. The SURMOUNT-5 head-to-head trial (NEJM 2025) showed tirzepatide produced 20.2% weight loss vs 13.7% for semaglutide at 72 weeks — a 47% greater relative reduction. Tirzepatide had fewer GI-related discontinuations (2.7% vs 5.6%). Semaglutide still has the larger cardiovascular outcomes dataset (SELECT trial), so a patient's comorbidity profile can tip the choice. See our comparison article for a detailed breakdown.

The most common are gastrointestinal: nausea (18–33% during titration), diarrhea (~20%), constipation (~11–14%), and vomiting (~8–13%). These are largely dose-dependent and improve with slower titration. Rare but serious risks include pancreatitis, gallbladder disease, worsening of diabetic retinopathy with rapid glycemic improvement, and a boxed warning for medullary thyroid carcinoma based on rodent data. At comparable efficacy, tirzepatide's GI discontinuation rate is roughly half that of semaglutide.

Indefinitely, if the indication persists. Tirzepatide is a chronic therapy for chronic conditions — both diabetes and obesity are relapsing-remitting. Discontinuation studies show that weight regain begins within weeks and continues for at least a year. A SURMOUNT-4 withdrawal substudy demonstrated that stopping tirzepatide after 36 weeks led to regaining about 14% of body weight over the subsequent 52 weeks, while continued treatment produced additional weight loss.

As of April 2026, large-scale compounding of tirzepatide is not FDA-permitted. Tirzepatide was removed from the FDA drug shortage list in late 2024, and the enforcement deadline for compounders expired March 2025. LillyDirect now offers self-pay vials directly from Eli Lilly at a lower cost than pen injectors, which has reduced — but not eliminated — demand for compounded versions. 503A patient-specific compounding remains possible under narrow clinical circumstances.

All weight loss — pharmacologic or behavioral — includes some lean-mass component. SURMOUNT-1 body composition data showed approximately 34% fat mass reduction and 11% lean mass reduction at the highest dose — a roughly 3:1 ratio favoring fat loss, which is more favorable than typical dietary weight loss. Resistance training and adequate protein intake (≥1.2 g/kg/day) further reduce lean-mass loss.

Tirzepatide activates two incretin receptors (GIP and GLP-1) while semaglutide activates only GLP-1. The GIP contribution appears to add appetite suppression through distinct central pathways, enhance β-cell function during hyperglycemia, and affect adipose tissue directly. Mechanistically, the dual action produces additive effects on glucose control and weight — and may also blunt the GI side effects that limit GLP-1 monotherapy dosing.

No absolute contraindication, but cautions apply. Tirzepatide slows gastric emptying, which can prolong and intensify alcohol's effects. Emerging observational data suggest incretin therapies reduce alcohol craving — some patients report spontaneously reducing intake. Heavy drinking increases pancreatitis risk, which is already a class-level concern. Most prescribers advise moderate drinking only, especially during titration.