my 5 yr old son has ADHD and High functioning autism as well. He is also very violent and agressive. He has been on Focalin Xr 15mg since he was 4yrs. It helps alot. He has also taken Risperdal at age 4yrs which worked like a miracle drug for him however his father who is not in the home threw a fit about the Risperdal so he is not taken it at this time.
There is no simple answer if, indeed, your son displays the conditions you describe. However, it is reasonable to focus on what might be called 'symptom reduction' - i., lessening of the aggression and volatility. Generally speaking, symptom reduction is achieved through pharmacological treatment. While use of medications with children so young is approached in a very conservative manner, it is possible to employ medication with a child as young as your son is. Specifically, it would be very reasonable for you to speak with his providers about using Risperdal, a medication approved for use in the treatment of autistic-spectrum disorders with children as young as five years of age.