Don't worry about it, that was rude of PoisonDurban given the situation. 'swim' is almost always used with the best intentions until someone points out why not to use it and then people cease.
It sounds like he could really use an anti-psychotic... I would be sort of surprised if a psychiatrist doesn't put him on seroquel risperidone or olanzapine or something right away... seems preferable and a good strategy to stop his induced / triggered psychotic sounding symptoms and also knock him out so that he can get some rest and even from just that chill out some more when awake... preferable to, say, him getting committed and put on haldol for becoming a danger to himself or others.
.25 mg of xanax is a pretty low dose especially for that state of mind, starting low isn't bad at all but stopping low might not be giving it a real shot. Again: would still go slow with it since the sedation might be confusing (not super likely), you might also prepare for him rejecting taking the meds because of delusions of being poisoned. Then again he must have appreciated getting a little sleep... May very well appreciate more in the meanwhile and it does suggest he tolerates it well, as in most cases probably.
Bipolar episodes? I am not sure that's really it, he might just alternate between being panicked because of the psychotic symptoms and too tired to be panicked? Though also I guess delusions can be conductive to mania and the big swings are like the ones possible during a trip.
Other than that... anything to ground him might help, if you're a parent and not the person in question you might try to arrange something that is comfortable and safe and brings back good and old memories. Maybe not go down memory lane all the way as that might be tricky, but you ought to know some simple things that have always been pacifying since he was little? Just something to help bring back feelings of things being alright and uncomplicated to step out of the ideations.
He probably wants to be alone like in his room, as a reflex to have a controllable environment... but just like it can be horrifying to try and go to sleep when you're having a bad trip (since you will basically just go deeper within yourself), so may staying in his room be a little too conductive to him going deep within himself. If you can, try to make that much less deep by offering items or an environment that aren't threatening or imposing, but well anchored in the reality that extends far beyond him and his room.
Before you go overboard with anything, check stuff I said against your personal situation... what is a smart move of course depends on your relationship with him, in part. Since that will determine whether he is likely to be threatened or imposed upon by you or feels loved and supported in the first place.
Good luck, I suggest that I move this to The Dark Side forum where you may find proper support during such difficult times, or alternatively Mental Health if you prefer which may focus more on the psychology and psychiatry I guess. This is not really primarily about psychedelic drugs even if they were the trigger.