Daniel Hulshizer/AP
Merck & Co. headquarters in Whitehouse
Station, N.J.

FDA Adds to Problems for Merck’s Asthma Drug Singulair

June 16, 2009 06:30 PM
by Denis Cummings
The FDA has requested that warnings of mood changes and suicidal behavior be placed on the label of Singulair, which is also facing challenges over the validity of its patent.

FDA Requests Warnings on Prescribing Labels

In a release posted Friday on its Web site, the Food and Drug Administration requested that the manufacturers of several asthma drugs include a precaution on the prescribing label “regarding neuropsychiatric events,” including aggression, anxiousness, depression and suicidal behavior. The drugs named are Singulair, Accolate, Zyflo and Zyflo CR.

The FDA has been investigating the drugs since last spring, following reports that Singulair patients had exhibited mood changes and suicidal behavior, and in some cases had committed suicide. Singulair, Merck and Co.’s top-selling drug, has been on the market since 1998 and had not been shown in Merck’s clinical trials to increase the risk of suicide.
Subsequent tests of Singulair, Accolate, Zyflo and Zyflo CR by the FDA also did not detect problems with suicidal behavior, though “they were not designed to detect such problems,” reports The Associated Press.

Merck already has warnings of mood changes and suicidal behavior on its label under possible side effects. The FDA is now calling for the warnings to be displayed more prominently on the label. “We did move this language to the ‘precautions’ section to highlight that we’re continuing to see these things,” said FDA spokeswoman Karen Riley to the AP.

Background: Patent concerns over Singulair

Singulair had $4.3 billion in sales last year, accounting for 18 percent of Merck’s total sales, according to Dow Jones.

Morningstar analyst Damien Conover told Reuters that the FDA’s announcement will only be a “slight negative” for Merck, because sales of Singulair have already been affected by news of the drug’s psychiatric side effects; sales of the drug fell 4 percent in the first quarter, reported Reuters.

A more pressing concern for Merck is the status of its patent for Singulair, set to expire in 2012. Teva Pharmaceutical Industries Ltd. challenged the validity of the patent in a court case, and last month the U.S. Patent and Trademark Office, responding to evidence presented by firm Article One Partners LLC, determined that the patent should be re-evaluated, reported Dow Jones.

When Merck loses its patent—whether in 2012 or earlier—it will face competition from generic versions of Singulair, known as montelukast. Teva is ready to sell its generic drug, and last month Mylan Inc. received tentative approval from the FDA for its generic form.

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