Help! Dealing with a child with ADHD

Im A mom of a 4 yr , we adopted he through the fostercare system and she was drug affected, she has just been diagnosed with ADHD and is on her 4th type of medication, we are very frustrated with the out comes of the meds.  Has any one else have any problems with finding the right kind of meds for the ADHD?  They tell me that since she was drug affected in utero with high levels of meth that the chemical is dificult to find and take care of..Any one else hear about this?  Or is the chemical the same? There are times that she is sooo agressive that i just want to cry, she talks all the time and sometimes just walks in circles.  Her therapist said that she is impulsive and compulsive and she is.  It is realy hard to be the mom i want to be with her and i know my husband feels the same way. If anyone has any suggestions I more than welcome them all!