Hi there. Welcome.
Ok...questions.
Did you adopt this child and, if so, at what age?
Did his biological mother drink or use drugs (or both) while she was pregnant? Was he abused? Thrown around from person to person? There is something most older adopted kids suffer from--attachment issues. It requires more than medications and is harder to work with than ADHD, but can manifest with or as ADHD.
Do you know if there are any psychiatric problems on his family tree on either side? These can be inherited so they can give you a clue as to what is going on...(Ok, I just re-read. With the history of bipolar, I think you need to consider he may have THAT. IF so, Adderall will likely make him worse...as will all ADHD medications, including Straterra...)
What behaviors are you seeing?
Do you know how his early development was? How is his eye contact, imaginative play, interactive play with peers? Can he transition well? Any sensitivities to sound, light, food, textures? Does he have an odd, repetitive mannerisms or vocalizations, such as high pitched screeches or silly mouth noises? Is he affection, cuddly?
What type of doctor diagnosed him? Here in the US, NeuroPsychs are very popular (and good) diagnosticians. They test for many long hours and look into everything. I don't know if you have that option in Canada. If so, take it!
The more you tell us, the more we can help. I'm a layperson, like all of us, but I'm guessing that, with his background, more is going on than ADHD. Are all of your kids adopted? I have adopted four children.
Welcome aboard!