FDA approves Zepbound, giving tirzepatide a second brand name for weight loss

On November 8, 2023, the FDA approved Zepbound (tirzepatide) for chronic weight management in adults, creating a second U.S. brand name for a molecule that had already been on the market since 2022 as Mounjaro for type 2 diabetes ^[5].

Tirzepatide was first approved in May 2022 under the brand name Mounjaro to improve blood sugar in adults with type 2 diabetes ^[5]. The Zepbound approval covered adults with obesity, or adults with overweight who also have at least one weight-related medical condition, and was based on the phase 3 SURMOUNT-1 and SURMOUNT-2 trials ^[5].

In SURMOUNT-1, which enrolled adults with obesity or overweight who did not have diabetes, people taking the highest dose, 15 mg, lost an average of 48 pounds over 72 weeks, and those taking 5 mg lost an average of 34 pounds, compared with 7 pounds on placebo ^[5]. In SURMOUNT-2, which enrolled adults with type 2 diabetes, average weight loss was 15.7% (34.4 pounds) at 15 mg and 13.4% (29.8 pounds) at 10 mg, compared with 3.3% (7.0 pounds) on placebo ^[5]. Lilly later described the 15 mg SURMOUNT-1 result as 20.9% of body weight, versus 3.1% for placebo ^[1].

Both names stayed on the market. IQVIA, a health data company, reported in September 2025 that Mounjaro and Zepbound were two of only three launch medicines ever to exceed $5 billion in sales in their first 12 months, alongside the hepatitis C drug Harvoni ^[2]. Nearly three years after Mounjaro's launch, it was selling about $3 billion a month, with Zepbound on track to pass that within a few months ^[2].

Lilly said in February 2026 that Zepbound was the most prescribed injectable weight-management medication in 2025 ^[1]. The company also announced an FDA label expansion for a four-dose, single-patient-use KwikPen, with every dose available at the same self-pay price through LillyDirect, starting at $299 a month for the 2.5 mg starting dose ^[1]. Lilly said one in three new patients starting a branded weight-management medication received Zepbound self-pay vials in 2025 ^[1].

In the same release, Lilly cited SURMOUNT-5, an open-label study in which people taking Zepbound lost an average of 50 pounds (20.2%) over 72 weeks, compared with 33 pounds (13.7%) for injectable Wegovy (semaglutide) ^[1]. Lilly notes that study collected data in a less rigorous way, so the findings are less certain, and that factors beyond the medications may have contributed to weight loss ^[1].

Why it matters for patients

Patients may hear the same drug called two different names. The name on the prescription reflects the approved use: Mounjaro is for adults with type 2 diabetes, while Zepbound is for weight reduction and long-term weight maintenance, and also to treat moderate-to-severe obstructive sleep apnea in adults with obesity ^[3][5].

Both products contain tirzepatide. The label says Zepbound should not be used with other tirzepatide-containing products or with any GLP-1 receptor agonist medicine ^[1][4]. It carries a boxed warning about thyroid C-cell tumors and is not for people with a personal or family history of medullary thyroid carcinoma, or with Multiple Endocrine Neoplasia syndrome type 2 ^[4]. Lilly states that Zepbound is not approved for people under 18 and is not for cosmetic weight loss ^[3].

Cost and access have changed since approval. As of February 2026, self-pay pricing through LillyDirect starts at $299 a month for the 2.5 mg starting dose, which is a starting dose only and not an approved maintenance dose ^[1][4]. Whether insurers treat the two brand names differently has not been reported here.

What has happened since

Tirzepatide's prescribing information lists an initial U.S. approval of 2022 and shows recent label updates, including a January 2026 change on never sharing a Zepbound KwikPen between patients and a February 2026 update on severe gastrointestinal reactions ^[4]. Lilly's June 2024 open letter said Mounjaro and Zepbound are the only FDA-approved tirzepatide medicines, and that products sold simply as "tirzepatide" — including compounded versions — are not FDA-approved ^[3]. How the two-brand structure affects coverage decisions, prior authorizations or pharmacy stocking has not been disclosed in these materials.