Thanks for the query.
To prepone the periods you have to plan at-least 15 days before your expected date of periods.
You have to take the tablets for 5 days.
After stopping the tablets usually in 4 to 5 days you will get withdrawal bleeding.
And you may get the bleeding for around 5 days.
If you are not having that much time, better to postpone the periods.
For that you have to start the tablets 5 days before expected date of periods and has to continue till the date you want to postpone the periods.
Usual side effects are nausea
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429