When to take antiemetic, and how much, for maximum efficacy?

[hematomatema]

I'm aiming to CTB in around 9-10 hours since that's when I get the best time alone where no one will find me in time, and I'm only doing it now because my domperidone finally arrived. Only issue is, I don't know how much to take and when. I don't want to take too much cause I've heard of some side effects that come from an OD that would make it an emetic rather than an antiemetic, and I don't want to take it too early/too late so that I can get the best effects from it.

Does anyone know when to take antiemetics before your method?