We now have our son on an inhaler called Xoponex....we only give it to him when he absolutely needs it which is like every couple weeks....he has mild asthma. He has not displayed the same behavior after taking him off Singulair.
I think anything but Singulair would be a wise choice. It's my opinion this is on BAD drug for kids. Our 5 yr. old son displayed some very agressive behavior, self loathing, very emotional, anxiety, didn't want to go to school, leg cramps, very restless, night terrors, etc, etc. After two days off Singulair he was back to his normal self. Good luck!!