Your child is displaying very disturbing behavior and as you said his medication treatment is not currently effective. Medication might ultimately be a part of his treatment plan but at this time, medication alone does not seem to be the correct treatment. Also, three years old seems very young for a child to be taking medication. In fact, according to the Food and Drug Administration (FDA), the drug Metadate has not been studied in children under the age of six. This means that currently the effect of Metadate on children between the ages 0-6 remains unknown to the scientific community.
It’s time for a new approach. Try taking your child to a child behavior specialist for intensive therapy and/or a mental health professional that specializes in family therapy. He or she can teach you and the rest of your family more appropriate ways to handle and respond to his behavior. This is a problem that needs to be addressed immediately because as he ages, these problems may increase. It would be difficult, for instance, to have him attend school if he is displaying these types of aggressive behaviors. Please contact other types of mental health professionals (as mentioned above) and avoid professionals who want to use medication as the only form of treatment for your son. This problem requires more than just medication. I hope this helps. Take care.