I started taking Singulair about a year and half ago. Six months ago I started having muscles twitching in legs and arms as well as other parts of my body. I have had 2 EMG's ans 3 MRI's and the doctors can not find any reason for the problems. I also have some muscle weakness in arms and cramps in the lower legs. Has anyone else had this type of reaction while taking Singulair? Please report if you have.