WHITEHOUSE STATION, N.J. (AP) — Drugmaker Merck says it plans to reduce its global workforce by another 8,500 jobs as part of a plan to cut its annual costs by about $2.5 billion by the end of 2015.

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The latest workforce reductions come on top of about 7,500 in previously announced job cuts. The two rounds of cuts means it is slashing about 20 percent of its workforce currently at about 81,000 people.

Merck & Co. says the cost cuts will allow it to better target its investments on the areas with the most potential for returns.

Of the $2.5 billion in cost savings, the company says it expects to realize $1 billion by the end of 2014.

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Most of savings are expected to come from marketing and administrative expenses and research and development.

The new restructuring program is expected to cut costs by between $2.5 billion and $3 billion.

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