Some very good points by specialmom. And yes, his age as well as the medications you have tried would help.
Yes, medications are different. They range from stimulant to non stimulant. From extended release to ones with a much shorter time span.
It certainly sounds like you should be getting some more information from your doctor. A very good overall coverage of AD/HD (meds, symptoms,behavioral help, etc) is provided by the book, "The ADD/ ADHD Answer book," by Susan Ashley. I can also give you online resources depending on the type of detail you want.
How old is your son? Perhaps he has been misdiagnosed and hence the medication isn't working as he does not have adhd in the first place? This does happen from time to time. For example, my son has sensory integration disorder which involves the nervous system and can look very much like adhd. He is 7 an dwas diagnosed at 4. Medication would not work on him. Instead, we do occupational therapy which includes activities specifically for his nervous system to calm him and keep him regulated as well as they work on behavior strategies. To date, we have no IEP at school and not had an issue in elementary school at all and few at home. I believe if he had been misdiagnosed with adhd/add ------------ this would not be the case.
I just bring that up because your post makes me wonder.
Tell me how old he is and I will try to give some suggestions on the aggressive and volatile behavior.