What are the legal and safety differences between compounded tirzepatide and FDA‑approved Zepbound/Mounjaro?
Executive summary
Compounded tirzepatide is a pharmacy‑made formulation that has not undergone FDA review for safety, efficacy, or manufacturing quality, while Mounjaro and Zepbound are FDA‑approved, commercially manufactured tirzepatide products subject to regulatory oversight and clinical trial data [1] [2]. Since the FDA ended broad allowance for compounding tirzepatide after shortages resolved, most compounding of tirzepatide is now unlawful and associated with increased legal and safety risks highlighted by manufacturers and regulators [3] [4].
1. Legal status: approved branded drugs vs. compounded pharmacy products
Mounjaro® and Zepbound® are FDA‑approved, branded tirzepatide products with indications and labeling that reflect agency review, whereas compounded tirzepatide is not FDA‑approved and historically was only permitted under limited shortage enforcement discretion—an allowance the FDA ended in March 2025, making most new compounding of tirzepatide illegal absent a documented medical necessity [1] [3]. Eli Lilly has pursued litigation and public warnings against sellers who market compounded or counterfeit products as if they were FDA‑approved Mounjaro or Zepbound, stating neither the FDA nor other regulators have reviewed many compounded products and that misleading claims violate the law [4] [5].
2. Regulatory oversight and manufacturing quality differences
FDA‑approved products are manufactured at scale under current Good Manufacturing Practices with batch testing for potency, sterility, and impurities; compounded drugs are made by individual pharmacies and are not subject to the same federal premarket review, batch release testing, or standardized pens and safety features used by the branded products [1] [2]. Compounding pharmacies are primarily overseen by state pharmacy boards rather than the FDA’s premarket approval process, which means compounding formulations can vary by facility in ingredients, dosage form, and sterility practices [6] [2].
3. Safety evidence and reported harms
Mounjaro and Zepbound underwent clinical trials that produced the safety and efficacy data in their labels; compounded tirzepatide lacks those standardized clinical data and therefore has no comparable evidence base for safety or effectiveness [2] [7]. Regulators and Lilly have reported contaminated or adulterated compounded products and warned that poor compounding can cause serious harm; media and company reports cite hundreds of adverse event reports and example cases including products with bacteria, impurities, or even inert substances masquerading as tirzepatide [5] [4] [8].
4. Formulation, dosing, and practical differences
FDA‑approved tirzepatide comes as prefilled sterile single‑dose pens with validated dosing increments and patient instructions; compounded versions have appeared in multiple formats—vials requiring manual syringe dosing, orally disintegrating tablets, or mixes with added ingredients like vitamin B12 or niacinamide—not present in branded products, creating variability in dosing, administration technique, and risk [2] [8]. Compounded options were often cheaper, which fueled demand during shortages, but that cost savings came with tradeoffs in consistency and regulatory protections [9] [10].
5. Conflicts of interest, agendas, and practical guidance
Pharmaceutical manufacturers and some providers emphasize safety and legal risks of compounding—understandably defending branded products and patient safety—while some compounding advocates stress access and affordability, asserting high standards at reputable compounders [5] [6]. The reporting shows both realities: quality variability and documented contamination incidents on one hand, and lower‑cost, serviceable alternatives provided by some pharmacies on the other [4] [6]. Given current FDA policy and the documented safety signals, patients and clinicians are advised to prefer FDA‑approved Mounjaro/Zepbound when available and to treat compounded tirzepatide as legally restricted and medically riskier unless a clear, documented medical necessity exists and compounding is done by a highly reputable source under strict oversight [3] [11].