Actually, I think maybe what JJJ was getting at is that Clonidine is actually something that slows down the blood pressure as well as proven to be a great thing for calming aggression. Matt was on it for quite awhile and it really helped. It might be something to consider if he already has some rapid heart beats, or heart issues.
Otherwise another dose of .5 of Risperdal in the morning might help. Unfortunately with Matt it made him just crash - and he is normally super hyper - but adding that in the morning just put him back to sleep.
He also tried Strattera which worked well for about a week, but then increased the aggression.
Of course these are just *my* stories - each child has his own metabolism and chemistry.
Good luck 
