Alliance Boots completed its two-part sale to Walgreen on Wednesday, putting buyout firm KKR on track to roughly quadruple the cash it invested in the European pharmacy company.

All told, the sale to Walgreen has put about £4.7 billion ($7.3 billion) in cash and stock in KKR's pocket, according to a person familiar with the matter. The private equity firm invested about £1.2 billion when it and other investors, including Alliance Boots executive chairman Stefano Pessina, took the company private in 2007 in the largest-ever European buyout.