The U.S. Food and Drug Administration said Tuesday it's continuing a safety review of Singulair and similar asthma medications to see if they are linked to mood and behavior changes including suicide.

The agency said the safety review, first announced last March, "may take months to complete."

The FDA previously said it was looking at post-marketing reports involving Merck & Co.'s (MRK) Singulair and asked the company to submit additional information. The agency also asked the manufacturers of drugs that work in a similar manner to Singulair to submit information. Accolate is made by AstraZeneca PLC (AZN) and Zyflo is made by Cornerstone Therapeutics Inc. (CRTX).

The agency said Merck submitted results from 41 placebo-controlled clinical trials in which 9,929 patients were treated with Singulair and 7,780 were treated with a placebo. One adult patient out of 9,929 patients treated with Singulair had suicidal thoughts and there were no completed suicides.

The FDA said AstraZeneca submitted results from 45 placebo-controlled clinical trials in which 7,540 patients were treated with Accolate and 4,659 were treated with a placebo. The agency said one patient in the placebo group attempted suicide and another thought about suicide. No patients on Accolate reported any suicidal behavior. The FDA said information submitted by Cornerstone showed no suicidal behavior in either the Zyflo groups or placebo groups.

The FDA said although it appears the data submitted by the companies would suggest the products aren't associated with suicide or suicidal behavior, it noted that the trials weren't designed to look at such behavior.

The agency said it was continuing to review clinical trial data to assess other neuropsychiatric events such as mood and behavioral adverse events related to the drug.

-By Jennifer Corbett Dooren, Dow Jones Newswires; 202-862-9294; jennifer.corbett@dowjones.com

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