Punishments symptoms and conditions

As a pediatrician I write for Singulair every day.
The medication is for allergies.
Allergies cause a cascade of event that I will describe:
adenoidal swelling, leads to snoring + sleep disturbances. Poor sleep makes the child tired the next day leading to less attentiveness, hyperactivity and eventually acting out.
Almost 4 out of five kids with allergies have those subsequent symptoms, and more.
Over the years the child poor behavior his parents, teachers and peers respond of criticism/ ridicule, and punishments, cause the child to feel inadequate, embarrassed, frustrated and eventually depressed and suicidal.

Yes, Singulair does cause behavioral change but they appear within the first couple of pills, the rest is due to allergies and lack of medical care, i.e. sleep, Singulair, and Zyrtec deficiency.
Allergy shots cause 4 times the incidence of suicidally than Singulair, and Ritalin 10 times more.
Check it, it's true.

My son has been taking singulair for three years--since he was two. It seemed to really help control his asthma (cough variant). He has recently become extremely violent--especially in school or with his baby brother. I did not realize singulair could be the problem. I also noticed he has been very moody and antisocial for the last year. We have tried extra attention, positive reinforcement, reduced and restricted tv/video viewing, modified diets, punishments--nothing seems to help the aggression. The only thing left we did not think about is the singulair. Any recommendations for taking him off? Is cold turkey ok, or better to decrease the mg (1/2 pill, then 1/4 pill, etc.) until he is off?