Lilly reports bacteria and impurities in compounded tirzepatide products
The test results raise questions about what patients actually get when they buy compounded or unapproved versions of tirzepatide, which are not FDA-approved.
Products sold as compounded tirzepatide have turned up with bacteria, unusually high impurity levels and, in some samples, a different chemical makeup entirely, Eli Lilly said on March 7 [1]. Tirzepatide is the active ingredient in Lilly's diabetes drug Mounjaro and its weight-loss medicine Zepbound, and the company said it is using the results to press regulators and state pharmacy boards to act against sellers [1][2].
Lilly laid out the details in an open letter, saying it had "deep concern" about products that present themselves as the real, FDA-approved medicines [2]. Some samples had a different chemical structure and a different color than Mounjaro or Zepbound, according to the letter [1]. "In at least one instance, the product was nothing more than sugar alcohol," Lilly wrote [1]. The letter was a republished version of one the company put out in January [2].
Lilly also stated that it does not sell or provide tirzepatide to any compounding pharmacies [1][2].
Compounded medicines are custom-mixed by pharmacies, usually at a lower price than brand-name products, and they face less regulatory review [1]. They are not FDA-approved [1].
The company has taken sellers to court. In the fall of 2023, it filed eight complaints in five states seeking unspecified damages, naming four compounding pharmacies and four medical spas and wellness centers [2]. One med spa advertised Mounjaro on its website even though Lilly does not provide the drug to it; the product was later removed from the site [2]. Lilly said it has sued medical spas, weight-loss clinics and compounding pharmacies over products claiming to contain tirzepatide [1].
The Alliance for Pharmacy Compounding, which represents compounding pharmacists and technicians, pushed back. "Lilly rightly notes that compounded drugs are not FDA-approved. But that fact does not mean compounded drugs are unsafe – any more than it means that FDA-approved drugs are always safe," CEO Scott Brunner said [1]. Brunner added that it is unclear whether the products in question were made by a state-licensed pharmacy, which can legally prepare a compounded version while the branded drug is in short supply [1].
Other GLP-1 makers have raised similar concerns. Novo Nordisk has sued sellers of products claiming to contain semaglutide, the ingredient in Wegovy and Ozempic, and reported in December that some compounded semaglutide samples were up to 33% impure [1]. Unauthorized Ozempic copycats sent three people to the hospital with hypoglycemia last year, the American Association of Poison Control Centers told Reuters in January [2].
Lilly has not disclosed how many products it tested, where they were bought, which laboratory did the work or how many contained bacteria [1][2].
Why it matters for patients
Tirzepatide is sold as Mounjaro and Zepbound, and Lilly says compounding pharmacies do not get the ingredient from it [1][2]. So a product advertised as compounded or generic tirzepatide carries no FDA sign-off on what is inside it, how pure it is or whether it is sterile [1]. The testing described in the letter found bacteria, elevated impurity levels, different chemical structures and, in one case, only sugar alcohol — a sign that whoever bought that particular product did not receive tirzepatide [1].
Legal compounding is a long-standing practice, and state-licensed pharmacies are allowed to make compounded copies while a branded drug is on the shortage list [1]. Part of the dispute is which products fit that description. The letter does not say how the tested samples were obtained, so whether any came from a licensed pharmacy has not been made public [1][2].
What happens next
Lilly said it will keep pursuing legal action against what it calls frauds, including certain medical spas, wellness centers and compounding pharmacies [2]. No court dates, state board enforcement actions or FDA steps tied to these test results have been reported [1][2]. Novo Nordisk's separate litigation over compounded semaglutide products is also ongoing [1].
Sources
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