Welcome to Just answer !
I am sorry to learn about the condition of your son and I empathize with you. Well it is really very tough at times to counter the behavioral component of MR, plus the anti psychotic drugs like haloperidol although effective but come with certain side effects which at times can compromise health of the child.
So I believe the safest anti psychotic with least side effects and decent efficacy in controlling ( not as effective as haloperidol but still effective enough ) behavioral component of MR is Abilify ( aripiprazole ) , to be started at low dose of 2 mg/ day as a single night time dose and after 1 week raising the dose to 5 mg / day and then after 10 days further upping the dose to 10 mg / day and then maintaining on this dose. At this dose the child is most likely to respond but gradual titration of the dose is necessary to let his body adapt to the drug at increasing dosage.
Also it is essential to discuss with his doctor about bringing him off haloperidol first by slowly tapering it's dose over course of 2 weeks and then starting him on abilify in the above mentioned pattern . Abilify usually does not cause weight gain and has safest side effect profile.
Kindly discuss this with his treating doctor and do the needful changes.
I hope this helps.
Wish you and your son all the best.
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