K4 symptoms and conditions

My four year old son has been taking Singulair for Astma and allergies for three monthes now. He has always been very bright, so when he could not answer simple questions, and started getting in trouble in K4 class, we wondered what was happening. We talked to teachers and were about remove him from the program. He has aggresive behavior, problems thinking or remembering, and generally crabby. He is complaining about night mares every night, and is tired. After reading all these comments, I think we are going to take him off and see how he acts in school. We will let you all know how things work out. Thanks for letting us know about Zyrtec, we will avoid this as well.