Merck & Co. said its Medco unit acted properly when it booked revenue from patient co-payments to pharmacies that it never collected, but its shares fell on a report that questioned the practice.
Shares of Merck fell $2.22 to $49.98 on the NYSE, their lowest level since late 1997.
Merck declined to comment on how the report about its Merck-Medco unit might affect the company's planned spinoff of about 20% of Medco through an initial public offering, which Wall Street expects next week.
