C.F.
It sounds like you have been through a lot with your son's condition. I am not sure how open you would be to try something different to help his situation besides drugs, so I am going to post the some advice that you can either use or at least look into before going any further.
I have a friend who has 3 children - 2 of which had siezures as a result of adverse vaccine reactions. They had been down the typical traditional medical route and were getting nowhere, except that their children's conditions were getting worse.
My husband is a natural healthcare provider, specifically trained in chiropractic, naturopathic, nutritional counseling and detoxification. He first evaluated the girls situations (hair analysis, etc.) to determine their toxicity levels - and found out they both had mercury and aluminum levels off the charts. He began them on a schedule of regular chiropractic adjustments, completely changed their diets (cut sugar, fruit, and grains) and started them on detox programs (ionic foot baths to get heavy metals out as well as activated charcoal and then adding a prescription grade probiotic in their diets as well as a really good fish oil - Nordic Naturals).
The thing you have to understand when you are trying to detoxify anyone is that it is kind of like an onion...toxins have built up layer upon layer and when you detoxify, you slowly peel the layers away - this results in things seeming to get worse before they get better - what is happening is that they are 'retracing' and once they go back through it, they won't go through it again.
End result: one of the girls after about a year of this is now siezure free - her last siezure was on 7/7/07 and she is literally a different child.
The other child was older and had sizures literally every hour...now she has an occasional siezure once a month or so...and is still working toward full recovery.
If you would like more information, please contact me. My husband consults many people over the phone - If you are looking for an alternative solution...it's not as easy as popping pills, but wouldn't it be worth it to have your child healthy again?
Just trying to help!
C.