Asperger’s Disorder is characterized by deficits in social interaction and repetitive behavior patterns that affect an individual’s functioning. Although symptoms such as overactivity and lack of attention are often present among individuals with an autism spectrum disorder, a diagnosis of ADHD is not made if Autistic Disorder is present. I recommend that you seek the assistance of an individual who specializes in the diagnosis of Pervasive Developmental Disorders because an accurate diagnosis can only be made through assessment by a qualified professional. An accurate diagnosis is important for identifying appropriate services and supports for you son. I also recommend that you seek the support of a Board Certified Behavior Analyst (BCBA), who would be able to conduct the appropriate assessments and to assist in developing a behavior plan to increase your son’s social skills. A BCBA can also help identify effective interventions for reducing your son’s problematic behavioral symptoms, which may reduce the amount of medication needed. Please visit the website of the Behavior Analysis Certification Board (http://www.bacb.com/) where you will find a directory of service providers.
Have you looked at the diagnostic criteria for Aspergers? You can google DSM IV Aspergers and see what the characteristics are. It is also common for child to have bits and pieces of different disorders. For example my son's main diagnosis is autistic spectrum disorder and he is considered high functioning because he has above average cognitive ability. But he can also be impulsive sometimes and have problems with focus and attenton which may be down to ADD.
As those with Aspergers tend to also have Sensory Integration Disorder - google that to see if it sounds like your son. This means any or all of his senses will be over or under senstiive. So he may have problems with bright sunlight, noise, smells, touch, taste, balance and co-ordination.
They also tend to have difficulties with Executive Functions - google that too.
I don't know about medications.
But I do know that having the right amount of support and the right approaches/strategies at school are going to lessen any behaviours considerably.
What is he taking the medication for? Tantrums (known as meltdowns) are very typical of being on the spectrum - it usually happens when they are over stimulated or when there is a change or something unpredictable happens.
You are entitled to another opinion. You can go to your GP and say that you think your son has Aspergers and ask for them to refer your son to a team of professionals that have experience in diagnosising this disorder.