Hello,
Well first off, Panacur if that is what you are using, only needs to be used once a week for a 2-3 week treatment.
Luckily, Panacur is not really toxic & "technically" you can give alot over what is actually dosed though of course it is not recommended.
He should be fine, but honestly, I do not think he will need anymore deworming treatment now as that should cover it.
What you need to do now is just keep his system flushed out well with water, by giving 2-4ml's daily for awhile. Watch for any strange behavior or any other changes in his eating patterns.
Tracie