Merck reported lower-than-expected first-quarter sales as generic competition hurt demand for its Singulair asthma drug, and the company cut its profit forecast for the full year.
After the earnings announcement, the company's shares fell in premarket trading. (Click here to get the latest quotes for Merck.)
Merck reported net income of $1.59 billion, or 52 cents per share, compared with $1.74 billion, or 56 cents per share, in the year-earlier quarter, when it took charges for $1.6 billion of acquisition and restructuring costs.
Excluding one-time items, the company posted earnings of 85 cents per share, down from 99 cents a share in the year-earlier period.
Revenue dropped 9 percent to $10.671 billion from $11.73 billion a year ago.
Analysts had expected the company to report earnings excluding items of 79 cents a share on $11.09 billion in revenue, according to a consensus estimate from Thomson Reuters.
Merck said its board had authorized additional purchases of up to $15 billion of the company's common stock, and that it would make repurchases of about $7.5 billion over the next 12 months.
Merck said it expected full-year 2013 earnings, excluding special items, of $3.45 to $3.55 per share. That is below the $3.60 to $3.70 it had forecast in February.
—Reuters contributed to this article.