UPDATE: Singular, Zyflo Asthma Drug Safety Review Continues

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.

Last March the FDA began a safety review of Singulair, made by Merck & Co. (MRK) to see if the drug was linked to behavior changes, suicidal thinking and suicide, and asked Merck and manufacturers of drugs of similar drugs - Accolate by AstraZeneca PLC (AZN) and Zyflo, by Cornerstone Therapeutics Inc. (CRTX) - to submit additional information. However, Tuesday the agency said that a safety review of the class of medications is ongoing and "may take months to complete."

Singulair, first approved in the U.S. in 1998 is Merck's top-selling product and had $4.3 billion in sales in 2007 and is the dominant drug in its class. The product is approved for use in children and adults ages 12 months and older as an asthma and allergy treatment.

The FDA 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.

In a statement, Merck said it "agreed" with the FDA's statement that the clinical data suggested Singulair wasn't associated with suicide or suicidal behavior. Singulair's label already discusses post-marketing reports of reports of suicidal thinking and other neuropsychiatric events like depression.

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 and has "not yet reached a definitive conclusion regarding the clinical trial data on mood and behavioral adverse events associated" with the three drugs.

- By Jennifer Corbett Dooren, Dow Jones Newswires; 202-862-9294; [e-mail]

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