Picolax - how fast does it make you run?

[deni]

OK guys this is a little embarrassing, but my clinic instructed me to take this soluable drink called picolax (laxative) to prep for the EPU on Friday, tomorrow at 4pm. Since I'll be taking a bus home around 4.30, and it's an hour's ride, I'm wondering - how soon does it start to work, and will I be risking major embarrasment if I take it before getting on the bus??

Or is my imagination running away with me??