Two recent studies on tirzepatide detection in breast milk - Awaiting final papers

It appears two different studies have recently been run attempting to detect and quantify tirzepatide in breast milk and were unable to reliably do so. One was run by Lilly and is reported on the clinical trials website, and another was run by a 3rd party - possibly Texas Tech - using milk samples from the InfantRisk Center (IRC) Human Milk Repository and funded by the Laura W. Bush Institute for Women’s Health.

It is important to note that the max dosage either studied was 5mg.

The Lilly study had 11 participants and just tested 5mg, while the Texas Tech study had 5 donors using doses ranging from .5-5mg.

Lilly trial with results posted: https://clinicaltrials.gov/study/NCT05978713 (No paper yet.)

Preprint paper from Texas Tech: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=5387250

Neither study was able to get strong enough results to reach the “level of detection” threshold.

The Texas Tech study said they could identify traces of tirzepatide in their high resolution mass spectrometry, but it never met the thresholds for either “level of detection” or “level of quantification”.

According to DuckDuckGo AI: “The limit of detection (LOD) is the lowest concentration at which an analyte can be detected but not quantified, while the limit of quantification (LOQ) is the lowest concentration that can be reliably quantified with acceptable precision and accuracy. Essentially, LOD indicates the presence of a substance, whereas LOQ provides a measurable amount of that substance.”

This is great news and hopefully the pre-print paper will complete its peer review successfully.

Here is the conclusion from the Texas Tech paper: “Assuming milk concentrations at the LOQ, the calculated relative infant dose was below 0.05%, significantly below the commonly accepted 10% safety threshold. These findings suggest that tirzepatide transfer into human milk is minimal and unlikely to pose a clinically relevant risk to breastfeeding infants. Further investigation in larger cohorts is warranted to validate these preliminary results and assess infant exposure and associated developmental outcomes.”

The good news is that the Lilly trial seems to validate these results.

The NIH is already referencing this paper in their tirzepatide entry in the Lactation Database: https://www.ncbi.nlm.nih.gov/books/NBK581488/

Hopefully we’ll see movement in official guidance on breastfeeding and tirzepatide in the future.

Here is the current Lactation database summary:

• Preliminary evidence indicates that tirzepatide is barely detectable in breastmilk with doses up to 5 mg. Furthermore, absorption by the infant is unlikely because it is probably partially destroyed in the infant's gastrointestinal tract. If a mother requires tirzepatide, it is not a reason to discontinue breastfeeding. Until more data become available, tirzepatide should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant.

For comparison, here is their summary on Semaglutide:

• Semaglutide was not detectable in the milk of mothers taking the drug subcutaneously. Their breastfed infants experienced no adverse effects. Some brands of oral semaglutide, such as Rybelsus, contain the absorption enhancer salcaprozate sodium, which may enter milk and accumulate in infants. Only injectable forms of semaglutide should be used during breastfeeding.

Note: I checked it out and the sema study the NIH is referencing here is also based on a small # of subjects (8 in this case).