Private equity firm KKR & Co. has formally approached Walgreens, the Illinois-based drugstore giant valued at $56 billion, with $16.8 billion in debt, with a proposed leveraged buyout. The deal may be the largest leveraged buyout in history, as Walgreens looks to remain competitive with CVS Health and others. Though Walgreens remains the largest retail pharmacy in the U.S. and Europe with more than 18,750 stores in 11 countries, a buyout would allow Walgreens to adapt to the rapidly changing retail landscape without the constant scrutiny from public shareholders.