I keep hearing different answers on caffine and phen. Does caffine make phen ineffective? My Dr told me just not to drink coffee for the first couple of days but it's been over 2 weeks and I'm dragging myself through the day. I had a pepsi yesterday just to get through a big day and didn't have any palpatations or anything. My heart doesn't race with the phen at all. But I don't want to do anything to make the phen not work. Please let me know what you think. Thanks!!