Kroger pharmacies are once again back in Express Scripts’ network, two years after the grocer kicked the massive pharmacy benefit manager to the curb over its allegedly unsustainable pricing model.

NEW YORK (AP) -- Express Scripts Inc. said Monday that it completed its $29.1 billion acquisition of Medco Health Solutions Inc., creating the largest pharmacy benefits manager in the country by far.

A small mail-order pharmacy, which ships presorted packets of medicines to its customers, is waging a David-versus-Goliath battle with Express Scripts, the nation’s largest pharmacy benefits manager.