I am a 56 year old man who has been suffering of asthma for sever...

I am a 56 year old man who has been suffering of asthma for several years. This spring my doctor put me on Singulair as an additional medicine to my cortisone-inhalator. After one month I have the same experience as many here has told about - depression and periods of "swinging mood", ups and drastical downs. AND - a growing problem with feeling in my fingertips, seem that with accelerating speed i am loosing feeling in fingertips and now even the hold fingers and parts of my hand, which feels "cold". Anyone here who recognize these symptoms?