The medicine Singulair, are the side effects more dangerous than they let on

The Food and Drug Administration said Thursday it is investigating a possible link between Merck's best-selling Singulair and suicide. FDA said it is reviewing a handful of reports involving mood changes, suicidal behavior and suicide in patients who have taken the popular allergy and asthma drug.

Merck has updated the drug's labeling four times in the past year to include information on a range of reported side effects: tremors, anxiousness, depression and suicidal behavior.

With sales of $4.3 billion last year, Singulair is used by millions of patients in the U.S, according to Merck. First approved in 1998, it's part of a class of asthma and allergy drugs that includes AstraZeneca's Accolate and Critical Therapeutics's Zyflo.

FDA said it is also reviewing reports of side effects with those drugs. Their labeling does not contain language about suicide

This is just scary. My son was on this medicine not even 6 months ago, because he gets signs of asthma everytime he gets sick. I took him off the medicine because of the way he was acting. The doc had told me that he might get moody from it. Well he ended up going after me, mind you he's only 6. I called my mom and she said to just watch him the next few days while he was on the medicine. Well than he went after me again. It was like this dark side of him I had never seen before, his eyes glazed over and he didn't realize what he was doing till after he did it. I stopped giving him the medicine right after that. It's scary cause so many kids are on this medicine.