Washington - The Food and Drug Administration says it's investigating a possible link between the allergy drug Singulair and suicide.
FDA said it is reviewing reports of mood changes, suicidal behavior and suicide in patients who have taken the drug. Singulair was drug maker Merck's best-selling product last year.
In the past year Merck has updated the drug's labeling four times to include information on tremors, anxiousness, depression and suicidal behavior reported in some patients.
Singulair had sales of more than 4 billion dollars last year.
Merck shares had fallen by 10 cents in late morning trading.