One way many docs detox benzo addicts is to change them over to a longer acting benzo (klonopin) and then taper down slowly. Doing an "on your own" benzo detox is just asking for trouble. You say you want your brother safe...get him to a doctor first thing tomorrow morning.
if he is down to either .5 or .25 mgs a day he will have no lethal or terrible wd effects from going cold turkey from the xanax..if he was above 2mgs i would say to taper longer and not go CT but he is at a very very low dose and he will be fine going cold turkey now that he has tapered down so low..he will only have the mental wd from going cold turkey, he will have cravings, anxiety and mild insomnia, so see about finding some hydroxyzine(a older generation anti-histamine, that most docs put you on when you are low enough on a benzo to replace going cold turkey, it is a muscle relaxant, mild euphoriant, and mainly anti-anxeity drug, it is very effective, many patients happily have switched over from 1mg xanax to 50-100mg hydroxyzine)..i had to do it and it worked well...if they dont use hydroxyzine then they will usually use a long lasting benzo to replace the short acting benzo but the dose hes at is so low it would only prolong him getting off and be playing with fire causing another possible addiction, so his best bet is to go cold turkey once out of xanax then go to the doctor then get hydroxyzine or some soma a anti-anxiety/muscle relaxant, and then for sleep OTC sominex or unisom will work fine and he would only have 5 days at most minor discomfort and trouble sleeping, it really will be all mental, it wont be bad at all trust me ive been thru it many many times-christos
Maybe .25 tomorrow and then skip 1 day and .25.