:^/ It seems like forever since I've played, but if I recall correctly, you just have to return to the main room of Toan's house. There will be a cut scene which will show Toan's mother noticing that the kitty cat has followed Toan home. You give the potion to her once you're in Toan's bedroom.
;^) Heh. I recall that on his second play through for the game, my brother tried his darndest to give the potion to the llama, to see what would happen. Nope; the game wouldn't let him do it....