Ozempic, Wegovy, Mounjaro, Trulicity, Zepbound — What the Labels Say About a Class That Reshaped Medicine in Five Years

The Package Insert series

A note on language

This series reads what the FDA-approved prescribing information actually says, in the terms the labels themselves use. Those terms come from conventional pharmacology and immunology — antibodies, immune response, autoimmune, immunogenicity, and similar. I do not accept that vocabulary as a description of what the body is actually doing, and readers of my other work know the reasons.

I use the terms in these installments for a specific reason: the strongest critique of a pharmaceutical label is almost always the label’s own words, measured by the label’s own methods, admitted by the label’s own manufacturer. Softening the terminology loses the force of the admission. When a label reports that 51% of patients developed antibodies and then admits it cannot characterize the effect of those antibodies, the reader should see both halves in the label’s own language. The measurement and the admission belong together.

Whether the framework producing the measurement is the right framework is a separate question, discussed elsewhere.

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In the clinical trials submitted to the FDA for Mounjaro, the manufacturer’s assays detected what the label calls anti-tirzepatide antibodies in 51% of treated adults — 2,570 of 5,025. In the trials for Zepbound, the figure was 64.5% — 1,591 of 2,467. A substantial share of what was detected cross-reacted with the patient’s own GLP-1 and GIP — the hormones the body uses to regulate appetite, insulin, and digestion. The labels report the findings and state that no clinically significant effect has been identified, while noting that available evidence is insufficient to characterize the effects on pharmacodynamics, safety, or effectiveness.

The five top-selling GLP-1 drugs in the United States — Ozempic, Wegovy, Mounjaro, Trulicity, and Zepbound — share a boxed warning for thyroid cancer in rodents whose human relevance “has not been determined.” They share a pattern of embryofetal abnormalities in rats, rabbits, and monkeys at clinically relevant exposures. They share warnings for pancreatitis, kidney injury, gallbladder disease, severe GI reactions, hypersensitivity, diabetic retinopathy, and pulmonary aspiration during anesthesia — the last added in 2024 and 2025, with the labels admitting they cannot yet tell doctors how to mitigate it. Wegovy carries warnings for heart rate increase and suicidal ideation that Ozempic does not, despite containing the same molecule. Zepbound had a suicidal ideation warning and removed it in February 2026. These are statements from the FDA-approved labels, written by the manufacturers, reviewed by the regulators, and filed with the agency.

This is the fourth installment in The Package Insert, a paid subscriber series that reads FDA-approved prescribing information for major drug classes. The five drugs here — Ozempic and Wegovy (semaglutide, Novo Nordisk), Mounjaro and Zepbound (tirzepatide, Eli Lilly), and Trulicity (dulaglutide, Eli Lilly) — were approved between 2014 and 2023. More than a tenth of American adults have now used one. Everything that follows comes from their package inserts. If you’re currently taking a GLP-1, considering one, or have a family member on one, this is the installment to start with.

Behind the paywall:

• Why more than half of tirzepatide patients develop antibodies against the drug

• How Ozempic and Wegovy, the same molecule, differ in which risks they disclose

• The warning Zepbound removed in February 2026, and the one Wegovy still carries

• What the labels admit about the mechanism of cardiovascular, kidney, and MASH benefit

• Thyroid C-cell tumors in every rat study, and the identical sentence in all five labels

• Consistent female-rat fertility findings, and how the labels explain them

• Why tirzepatide labels tell women on oral contraceptives to switch methods for four weeks after each dose change

• The pulmonary aspiration warning the labels admit they don’t know how to mitigate

• The Wegovy fracture signal in women and patients over 75

• Why injection site reactions in antibody-positive Zepbound patients were eleven times the rate in antibody-negative patients

• Questions to take to your doctor — integrated throughout and consolidated at the end