asthma
"Singulair is an effective medicine -- but can have significant side effects.  I experience a foggy head and depressed mood.  I have also experienced muscle cramps in my back while on this.  I have noticed in reading through the comments that quite a few people are suffering with some for of side effect from this medicine.  One recommendation:  I talked to my doctor about cutting he dose in half, from 10 mg to 5 mg.  I now take a childrens 5 mg tablet.  I still get relief but don't experience the same level of side effects."