Merck stockholders received 0.1206 Medco common shares for each Merck share they held on Aug. 12. Shares of Medco were recently trading at $24.26, up 41 cents.
Medco had revenue of $33 billion in 2002, and last year it filled or processed about 548 million prescriptions.
Regular trading began today on the New York Stock Exchange for Medco's securities follows the distribution of 270 million shares to stockholders of Merck, which has owned Medco Health since 1993. Also with the opening day of trading, Medco joined the S&P 500.Shares of Merck were adding 41 cents to $51.25.