McKesson Corp. and CVS Caremark Corp. have extended their distribution agreement by three years.

CVS Caremark is McKesson's largest customer. The two companies had renewed their distribution agreement in 2013. Earlier this year, McKesson also announced an expanded relationship with another key drug chain customer, Rite Aid Corp.

SAN FRANCISCO — McKesson Corp. and CVS Caremark Corp. have extended their distribution agreement for pharmaceuticals.

McKesson said Wednesday that with the three-year extension, its distribution pact with CVS now runs through June 2019.

CVS Caremark is McKesson’s largest customer, accounting for about 16% of the pharmaceutical distributor’s total revenue in its 2014 fiscal year ended March 31.

"We have a long track record of delivering comprehensive supply chain solutions to CVS Caremark, which in turn allows CVS Caremark to ensure the highest level of pharmaceutical care to its customers," Paul Julian, executive vice president and group president at McKesson, said in a statement. "We are pleased to have extended our agreement with CVS Caremark and continue our long-standing partnership."

CVS Caremark and McKesson had announced a renewed distribution agreement in April 2013.

Also that April, Cardinal Health Inc. announced that it entered new agreements to supply pharmaceuticals to CVS Caremark’s retail pharmacies and distribution centers through mid-2016.

Earlier this month, the generic drug joint venture of CVS and Cardinal went operational. Called Red Oak Sourcing LLC, the Foxborough, Mass.-based venture is the nation’s largest generics sourcing entity. According to Cardinal, employees and functional responsibilities have transitioned from CVS and Cardinal to Red Oak Sourcing. Cardinal had announced the completion of the venture’s formation in May when reporting its third-quarter earnings.

CVS and Cardinal unveiled the joint venture in December. Plans call for the 50/50 venture to source and negotiate generic supply contracts with generics manufacturers for both Cardinal and CVS Caremark. The entity is slated to have an initial term of 10 years.

For McKesson, the extension with CVS marks the second major distribution agreement expansion with a drug chain this year. In February, McKesson and Rite Aid Corp. announced a new five-year agreement that runs to March 2019. Under the arrangement, along with brand-name pharmaceuticals, McKesson also now handles the sourcing and distribution of generic drugs for Rite Aid.