Birth control (ortho tri-cyclen lo) and cascara sagrada, which is a supplementof these have any dangerous side effects if I drink tomorrow night?

Diarrhea. Cascara sagrada is an herb that has laxative effects. Taking this with alcohol is likely to cause significant diarrhea. I dont think it will interfere with birth control pills unless you took it at the same time and your bowels flushed the pill through your system so fast that it couldnt get absorbed. Best not to take the cascara.