March 28, 2008 7:52 pm

Merck’s Singulair likely to see prescription drop-off only in high-risk populations

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Merck’s asthma and allergy drug Singulair may see a decline in prescriptions due to recent concerns about suicidality, but the drop will not be precipitous, physicians told Pharmawire.

The warning will likely cause the biggest prescription fall-off among patients with a personal or family history of depression, or patients with mild disease, they add. The drug is taken daily to prevent asthma attacks and allergies, or as needed for exercise-induced asthma.

”Both my kids are on Singulair - and I’m not going to take them off it,” said Dr Lawrence Ciesemier, an allergist and immunologist who practices Kirksville, Missouri. ”It was a surprise to me that this data came out.”

Dr Gregg Santilli, an allergist and immunologist in private practice at AirCare in Plano, Texas, noted that he has prescribed Singulair - a drug he helped launch - for 10 years without seeing any suicides. ”Apparently this is an extremely rare event,” he said. ”This drug has certainly not been linked in a causative way to this.”

”The real question is whether the [the number of suicides] is greater than what’s seen in the general population,” said Dr Jay Portnoy, president of the American College of Allergy, Asthma and Immunology. ”It’s still an extremely safe and effective medication.”

The FDA announced yesterday that it is ”considering” regulatory action after post-marketing reports seemed to link the asthma and allergy blockbuster to suicidal thoughts and action. Officials said in a statement that they are undertaking a nine-month review of Singulair and three other leukotriene modifying medications: AstraZeneca’s Accolate and Dey’s Zyflo and Zyflo CR.

Dr Douglas Bremner, director of Emory’s Clinical Neuroscience Research Unit, noted that drugs can cause psychiatric effects when the targeted receptor also exists in the brain. But he added that it’s unclear whether the brain has leukotriene receptors.

He noted that despite the updated label, the side effects ”sort of flew below the radar.” However, he painted a grimmer picture of the effect on the market, saying this [advisory] would affect Singular sales badly. People are likely to stop taking it, he added.

Over the past year, Merck has updated its safety label to include reports of tremors, depression, suicidality, and anxiousness, the FDA said.

But Dr George Philip, senior director in clinical research for Merck, noted that none of the reports of suicidality came out of clinical studies. He added that post-marketing reports can be ”sketchy” and ”not well-defined” - making it more difficult to determine whether the drug caused the change in behavior.

Asked about whether certain high-risk patients should avoid Singulair, he said, ”It may be part of the dialogue moving forward. These are still unanswered questions.”

He added that other allergy drugs have also been linked to suicide, including Pfizer’s Zyrtec.

Santilli noted that he would consider each patient’s individual risk factors - and the severity of their asthma - before making any treatment changes. GlaxoSmithKline’s Advair has a black box warning linking it to an increased risk of asthma-related death, he said, and Zyflo patients must be monitored for liver toxicity.

”Every drug has risks and benefits,” he said. ”Singulair seemed to be a very clean, very safe drug.”

Ciesemier agreed. ”I prescribe Singulair daily,” he said, but conceded that ”maybe this wouldn’t be the first choice” for patients with a history of suicidality.

Patients who are taking the drug for allergies, a less serious condition, might be more likely to switch to an antihistamine, Santilli noted.

Singulair earned USD 4.3bn last year, growing 19%, and is the bestselling respiratory product on the US market, according to the company. Merck has a market cap of USD 96.57bn.

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