My son was on Singulair for 3 yrs. I finally recognized the
side effects he was having and discontinued. He suffered from leg
pain, stomach pain, irritability, anxiety, quick to tears, easily frustrated and excessively fearful. At the age of 7, his dosage was increased to 5mg. At that point, it became very clear he was suffering side effects. All of the side effects I mentioned above were multipled x 10. He also began to have hallucinations, facial tics and night terrors.