I took my very happy, sweet, polite four-year-old son to the doct...

I took my very happy, sweet, polite four-year-old son to the doctor yesterday because he was coughing horribly during the night. Great during the day, hacking at night. He was put on Singulair. I didn't think twice about it, since I am on it and have had no problems (although I take it sporadically since I tend to forget!). I picked him up from pre-school today and was told that he was a completely different child. Rude, put in time-out multiple times, refused to listen. This is behavior that he has never had at school, and the only difference is the Singulair. I will not be giving that to him again!