Frequently asked questions

Is tirzepatide approved?

Yes, and that makes it unusual among the compounds documented on this network. FDA's substance record lists it as an INN, USAN and JAN and names two marketed brands, Mounjaro and Zepbound. What that approval covers is those products, made to their filed specifications. It does not extend to material sold under the same name outside that channel. source

Can a pharmacy still compound tirzepatide?

The lane that existed during the shortage has largely closed. FDA determined the shortage resolved, and enforcement discretion for compounders ended 2025-02-18 under section 503A and 2025-03-19 under section 503B. On 2026-04-30 FDA proposed excluding tirzepatide from the 503B bulks list, concluding there is no clinical need for outsourcing facilities to compound it from bulk substances. source

How long does tirzepatide stay in the body?

A population pharmacokinetic model pooling 19 studies reports a half-life of approximately 5 days. That measurement was made with the approved product in supervised studies, and both authors of the analysis are Eli Lilly employees and shareholders. source

Is the approved product the same as material sold for research?

No. An approval attaches to a finished product manufactured to a filed specification, including its excipients and packaging - FDA's label lists sodium chloride, sodium phosphate dibasic heptahydrate and water for injection alongside the peptide. Nothing in the trial, label or pharmacokinetic record describes material obtained outside that channel, and no independent analysis of such material was located during data entry. source

What is the difference between tirzepatide and retatrutide?

Receptor count, and regulatory status. Tirzepatide acts at two receptors, GIP and GLP-1. Retatrutide adds a third, the glucagon receptor. Tirzepatide is an approved drug substance in marketed products; retatrutide is not approved anywhere. They are different molecules with different formulas and separate literatures. source