WHITEHOUSE STATION, N.J. (AP) — Merck & Co Inc. said it will repurchase $5 billion worth of its common stock under an accelerated share repurchase agreement with Goldman Sachs & Co.

Merck, the world’s third-largest drugmaker, said the buyback program is part of a previously announced $15 billion share repurchase program.

In the first four months of 2013, Merck repurchased about 17.8 million shares for a total of $772 million.

Shares of Merck & Co Inc. rose $2.12, or 4.7 percent, to close at $37.33. Shares rose 52 cents to $47.85 in after-hours trading.