Eli Lilly cautions on safety concerns with tirzepatide compounded with vitamin B12 | iPharmaCenter

Eli Lilly and Company has released a public advisory highlighting possible safety issues with compounded formulations that combine tirzepatide and vitamin B12.

Also read: Top 10 Pharmaceutical Companies by Revenue 2025: Best-Selling Drugs Analysis

The testing revealed a chemical impurity generated by the interaction between vitamin B12 and compounded tirzepatide, and Lilly notes that there is no information on how this impurity behaves in humans over the short or long term. It is unknown whether this byproduct affects tirzepatide’s binding to GLP‑1 and GIP receptors, alters its toxicity profile, triggers immune reactions, or changes how the drug is absorbed, distributed, metabolized, and cleared from the body.

Because tirzepatide has never been systematically evaluated in combination with B12, and because compounders are not required to conduct clinical trials or robust safety monitoring, the overall risk to patients using these mixtures remains undefined.

Also read: FDA Grants Second Approval to Sotyktu in the US; approved for Adults with Active Psoriatic Arthritis

Lilly stresses that individuals obtaining tirzepatide‑B12 combinations from compounding pharmacies, telehealth platforms, medical spas, or other vendors may be exposed to products with untested and potentially hazardous properties.

Zepbound is a prescription injectable medicine containing tirzepatide that is approved for adults with obesity, or adults who are overweight and also have at least one weight‑related medical condition, to help reduce excess body weight and support long‑term weight management when used with a reduced‑calorie diet and increased physical activity.

It is also indicated for adults with obesity and moderate‑to‑severe obstructive sleep apnea (OSA) to improve their OSA, in combination with lifestyle measures such as diet and exercise.