Overview
- Lilly says analytical testing of 10 U.S. compounded tirzepatide+B12 products found a previously unidentified impurity formed by a chemical reaction in every sample.
- Some samples showed inconsistent potency—down to 43% of the labeled dose—and Lilly also reported bacterial contamination and elevated endotoxins in certain products.
- The company notes that the tirzepatide–B12 combination has never been studied in humans, leaving its effects on efficacy, toxicity, immune response, and receptor activity unknown.
- Lilly has notified the FDA and is urging a nationwide recall of compounded tirzepatide that includes untested additives such as B12, glycine, pyridoxine, niacinamide, or carnitine.
- The Alliance for Pharmacy Compounding challenged the announcement, seeking detailed methods and data, as the FDA reiterates past warnings on compounded GLP-1s and steps up enforcement against misleading marketing.