Lilly issues letter warning potential risks of compounded tirzepatide, B12

Lilly is issuing a public warning about potential safety risks associated with compounded tirzepatide mixed with vitamin B12. As part of the company’s commitment to patient safety, Lilly tested compounded products being marketed to Americans that contain tirzepatide combined with B12. Testing has uncovered significant levels of an impurity that results from a chemical reaction between tirzepatide and B12. The impurity caused by the interaction between B12 and compounded tirzepatide is concerning because nothing is known about its short- or long-term effects in humans, the potential impact on the drug’s interaction with the GLP-1 and GIP receptors, toxicity, immune reactions, or how it is absorbed, distributed, metabolized and eliminated. The risks to patients are unknown because tirzepatide has never been studied in combination with B12 and the compounders making these combination drugs are not required to monitor or report adverse events. People receiving tirzepatide-B12 products from compounders, telehealth companies, medspas, or anyone else should be aware that they may be using a potentially dangerous product with unknown risks. Lilly has notified the U.S. Food and Drug Administration about these findings and recommends that people using these untested products contact their physicians for advice and discussion on alternative treatment options.