McKesson Corp., the largest U.S. drug distributor, recently agreed to purchase PSS World Medical Inc. for about $2.1 billion. The acquisition will allow McKesson to deliver medical products to long-term care facilities. PSS World will be combined with McKesson’s existing medical surgical business and be part of McKesson’s Distribution Solutions segment. The $29-a-share agreement also includes the assumption of PSS World’s debt, San Francisco-based McKesson said in a statement.