Merck & Co. Inc.'s stock dropped 1.5% in midday trade Friday, after the drug maker disclosed in a filing late Thursday that it had received a civil investigative demand from the U.S. Attorney's office. The demand requests information related to the contracting and pricing of its Dulera Inhalation Aerosol asthma treatment with certain pharmacy benefit managers and Medicare Part D plans. Merck said in the filing that it was cooperating with the investigation. The stock has lost 4.5% year to date, while the Dow Jones Industrial Average has ticked up 0.1%.
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