Merck & Co said on Wednesday it plans to buy back up to $5 billion in shares, bringing its total share buyback program to $6.4 billion.
The Whitehouse Station, New Jersey-based drugmaker said the stock purchase has no time limit and will be made on the open market, in block transactions or privately negotiated transactions.

"Merck has a history of leadership in returning cash to shareholders," said Kenneth Frazier, Merck's chief executive officer. "Today's action reflects our confidence in Merck's strategy and demonstrates our commitment to delivering shareholder value."

The company still has $1.4 billion remaining from a share repurchase authorization announced in November 2009.