@megancmarsh and @LadyBBGoneCountry im linking a webpage that'll give u proper dosage as well
https://poultrydvm.com/drugs/ivermectin#:~:text=For chickens and ducks: 0.2,repeated in 10-14 days.
i get it from tractor supply and its a pour on type (which makes it a whole lot easier) red and yellow box usually behind glass over by the horse stuff
i used to bring my pet rabbit and rats everywhere. they will really only get stressed when they arent used to it or if they have a personality that doesnt want to do it. i had one bunny that wanted nothing more than to be everywhere u were and another that would rather lounge on the couch then...
if you dont want the rats dead you can deter them with pure peppermint oil on cotton swabs around entrances. if you want them unalived then theres 1 bite rat bait