Walgreen ends CVS Caremark network relationship

DEERFIELD, Ill. (AP) - Drugstore chain Walgreen says it will no longer be a provider in new or renewed prescription drug plans awarded to CVS Caremark's pharmacy benefit manager.

Walgreen says CVS Caremark's promotion of some plan designs disrupts networks by requiring patients to use CVS Caremark services. Walgreen also cited the growing unpredictability of CVS Caremark's reimbursement rates among other reasons for ending the relationship.

Walgreen says current CVS Caremark plans in which it is already a pharmacy provider will not be affected.

The Deerfield, Ill., company is the largest U.S. drugstore chain in terms of locations and revenue, slightly ahead of CVS Caremark.

Shares of CVS are dropping 5 percent in premarket trading.