I think this is a common thing in any child not just children on these med’s.  I have a particularly difficult two year old that doesn’t like to go to bed early, and I am finding it difficult at the moment because he cries and keeps the other children awake.  I give in after half an hour and take him into my bed.  I am actually thinking of putting him in his own room for a while (until he is settled into a bedtime routine) and just ignoring him when he cries, because the moment I take him into my bed, the little toad goes straight off to sleep because he has got his own way. :)