My daughter Ashley (9yrs SWCAH) was put on Dex several years ago.  But she takes her Dex every 12 hours, not once a day.  Maybe you should ask the endo if you could split up the dose so that he has it every 12 hours.  My endo also told me that if Ashley takes her am dose and 7am then the pm dose is to be at 7.  There are times when we have overslept and she did not take it until 8am but almost every day she takes it at 7am.  She has not complained of headaches but she did gain weight when she started the dex.  I also have her take her meds with her breakfast and at night with a cup of milk.

Hope it all works out with you and keep me posted.

Lisa V