Check this thread out, http://forums.studentdoctor.net/showthread.php?t=675270
It'll have most the information you are looking for. I don't know if I am allowed to tell you the essay topic, nor do I know if they change it for each batch of interviewees, but it is an ethical questions regarding how you would handle a specific situation in pharmacy school.
Also, interviewees are in groups of 5-6. They ask a questions and you can volunteer to answer it. SDN interview feedback will help you out alot too. Make a list of the questions posted in that section. Formulate appropriate responses and practice in front of a mirror or do mock interviews. Good luck!