I've got my first colonoscopy tomorrow too, but I was told to take my prep at 5pm and 7pm. I would think that if you threw it up, it's not working because it's not in your system. It might be a good idea to purchase another one just in case. Maybe try phoning again and hope you get someone other than the unsure receptionist. Or tell her you want to speak to the doctor (make sure he/she phones you back!) I think it's a good time to be persistent about this. Fiona