Weekly prescriptions for Merck & Co.'s asthma and allergy treatment Singulair plunged nearly 90% within four weeks of the August introduction of competing generic copies, a Merck executive said Tuesday. “There’s been a rapid decline and loss of sales,” Adam H. Schechter, president of Merck’s global human-health unit, told investors at a Morgan Stanley health-care conference in New York. Weekly prescriptions for branded Singulair declined 87% four weeks after the early August loss of U.S. patent protection for the drug, according to a slide presented by Mr. Schechter. The patent loss triggered the introduction of lower-priced, generic versions of the drug from multiple manufacturers including Mylan Inc. and Endo Health Solutions.
