You might consider the anti-epileptic drugs (AED).
These are also used as mood stabilizers. Drugs like: Depakote, gabapentin, Trileptal, Keppra, etc. These cut my agitation when it amps up.

The major tranquilizers may put your son at risk for Tardive Dyskinesia.

Continue to watch your son closely when attempting any med, as most of them can have some severe side-effects.

Thanks for being an interested parent! Not all parents look into treatment options and advocate for their children. So, thank you!

My Best,

WC