Express Scripts' proposed $29 billion acquisition of Medco Health Solutions is expected to face intensified scrutiny today when a Senate panel examines potential antitrust concerns raised by the merger of two of the country's largest pharmacy benefit managers. Together, the two companies now manage prescription drug benefits for more than 115 million people and handle one of every three prescriptions filled in the United States. With combined revenue of more than $110 billion a year, the merged entity would also become the largest player in the domestic markets for supplying mail-order drugs to patients with chronic conditions and costly specialty drugs for conditions like H.I.V., hemophilia and rheumatoid arthritis.
