Oh, dear. At least you did manage to get most of it down him eventually!

Would it, perhaps, be possible to dilute it in a larger amount of pudding? (I have no idea what a rat's, or Kieran's, stomach capacity is, but if it's larger than a teaspoon...) Or split between two teaspoons, fifteen minutes apart?

Best of luck either way! (Reading this, I keep thinking of the cat at work who's currently pink because guess what? he doesn't like the taste of his antibiotic, either.) :D