The syringe handle has notches on it - 1 notch for every 50#. It works the same way for humans. I push out the amount I want, put it in my mouth, then follow it with a glass (8-12 oz) of water. The directions I found somewhere say to take it on an empty stomach (I take it in the morning a while before eating).
I have a daughter who was taking it regularly. She had dermotagraphia, which means that just running her fingernail lightly across her skin resulted in welts that lasted half an hour or so. She no longer has that, and believes it was the ivermectin that healed that.