Singulair Side Effects: I was put on singulair in Feb of this year but the 5mg and it see http://www.medications.com/effect/view/30678 I was put on singulair in Feb of this year but the 5mg and it seemed to be helping. I went and saw an allergist and he put me on 10mg of singulair and i have been on it for 11 days. And I have had, stomacher pain, muscle pain and weakness and I feel out of I agree this medicine needs to go. Make sure to post your side e Wed, 21 May 2008 22:26:26 -0400 http://www.medications.com/effect/view/30678?item=8515 I agree this medicine needs to go. Make sure to post your side effects on fda.gov. It only takes a minute to fill out the form. I took singulair for 2 days and had the most horrific, terrifiying dreams. I immediately stopped the med. http://www.medications.com/effect/view/30678?item=8515