Is there a history of anxiety disorders in
the family as Social Phobia, Obsessive Compulsive Disorder
, Separation Anxiety
, etc. or other mental health issues? By the way, the fact your stepdaughter is throwing tantrums indicates severe frustration and this is one sign common to several mental health issues. Really, the first thing you need to do is discover the reason for this medication. Should not both parents be privy to this information? This, I feel, is your beginning point.