I have seen messages before about donating unused pet medications and the consensus seemed to be that all medications have to be destroyed. I also believe that to be the case until today! I found
https://wvs.org.uk/support-us/donate-medication/
who say
"Donate Medication: How your donation makes a difference
Donate unexpired, unused, or leftover medications, and we'll get the life-saving supplies to veterinary teams helping homeless animals, wildlife in need, and pets living in rural and often poor communities."
There is an online form to be filled in and they contact you in due course to say if they can accept your donation. It is such a shame that this isn't more wildly known, even our vet didn't know of it.