Delayed speech symptoms and conditions

I have a 26-month old grandson who has been on Singulair for "27 DAYS". His pediatrician knows that his immune system is already compromised due to some developmental delays. However, before he started taking his Singulair he was a very happy, funny and loving child. Within 2 weeks on this medicine we started to notice a few changes in him. He started waking up at night "screaming" and he has been sleeping through the night for at least a year now. And when his mother would go in to get him out of his crib, he would be so frightened and afraid to leave her side. It would take her a very long time to settle him down and put him back down for the night. At the same time, he started not wanting to drink his normal daily glasses of milk or eat his regular meals. He was simply a mess most of the day and would fuss, cry, bang his head and we were having a very hard time trying to figure out what was wrong with him. He is not yet talking due to his delayed speech, so he could not tell us what was going on. Yesterday, I told my daughter let's look at the side effects of Singulair since it was the only thing that had changed within the last few months. When I found this site, I could not believe what the parents/grandparents were saying about their children on this drug. We immediately took him off Singulair. This will be his second day without being on the drug. According to my pharmacist, it will take approximately 50 hours for it to get out of his little system. The pharmacist had not heard the latest that aired on the TV station, so she asked me to call her back in a few days to tell her how my grandson is doing. Parents should be able to trust the medications that are prescribed by their Pediatricians, especially at such young ages. My daughter is REALLY UPSET and has a call into my grandson's doctor. Thank God I found this website. I simply searched on "side effects of Singulair in children" and this site came up. I do believe the Lord is watching over my grandson. Thanks.