Singulair, Merck & Co Inc.’s top-selling drug, and similar medicines, should come with a caution about reports of psychiatric problems in some patients, according to the federal government. The Food and Drug Administration has requested a precaution in the prescribing instructions for Singulair, Accolate (AstraZeneca) and Zyflo and Zyflo CR (Cornerstone Therapeutics). Of course, a precaution is a less-serious alert than a warning. Problems that were reported to the FDA include agitation, aggression, suicidal thinking, suicide, depression, insomnia and irritability.

The FDA says that psychiatric problems were uncommon in clinical trials of the drugs but those data were limited because the studies were not designed to evaluate those issues. Some post-approval reports of psychiatric events “included clinical details consistent with a drug-induced effect,” the FDA added. The agency says that doctors should be aware that “mental issues could arise and consider discontinuing the drugs if patients develop psychiatric symptoms.”

Merck said in a prepared statement that it was confident in the safety of Singulair. It said the drug has been prescribed to tens of millions of patients with asthma and allergies since its approval in 1998. But the company said it would revise the drug label as requested.

The types of problems the FDA cited already were mentioned in a less-prominent section of the prescribing instructions. Singulair is Merck’s biggest product with annual sales of $4.5 billion. The drug’s generic name is montelukast. The FDA announced in March 2008 that it was reviewing safety data that raised concerns Singulair might be linked to suicidal behavior or mood-related side effects.

AstraZeneca says it is adding a precaution about reports of depression and insomnia to the label for Accolate, which had sales of $73 million worldwide in 2008. The drug’s generic name is zafirlukast. So far, officials at Cornerstone Therapeutics haven’t made any comment on Zyflo, known generically as zileuton.

Source: Reuters