Hi LJ,

It has been discussed before, but there's a dearth of research on its use in horses.  Just a quick lookup of 'use of tylenol in horses' in Google can bring up what's up what's been done/or not.  Basically it looks like there was an initial study in 2017 and it was found to work and then there was a follow up study in 2019 that showed that it can be given for 2 weeks with no ill effects on the liver (but those horses weren't lame, they were just looking at the medication effects): https://pubmed.ncbi.nlm.nih.gov/30900298/

You can read an entire thesis on it here: https://vtechworks.lib.vt.edu/bitstream/handle/10919/85379/Mercer_MA_T_2018.pdf?sequence=1&isAllowed=y