Walgreens Boots Alliance Inc. plans to repurchase as much as $10 billion of its shares and raised its dividend by 10%, as the drugstore chain and newest Dow component became the latest company to return additional capital to investors following the new U.S. tax law.

However, Walgreens shares fell 9.9% to $59.70 in Thursday trading after Amazon.com Inc. said it was buying online pharmacy PillPack Inc., a move that sent shares of pharmacy and medical-distributor companies tumbling.

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