Two retailers are joining a drug war against two major pharmaceutical companies.

CVS Caremark Corp. and Rite Aid Corp. yesterday filed an antitrust lawsuit against Pfizer Inc. and Teva Pharmaceutical Industries Ltd., accusing the pharmaceutical companies of conspiring to keep competing generic versions of Pfizer’s antidepressant Effexor XR off store shelves. Walgreen Co., Safeway Inc., Kroger Co., Supervalu Inc., HEB Grocery Co. and American Sales Co. filed a similar complaint in the same court this past November.

According to CVS and Rite Aid’s suit, Pfizer’s Wyeth unit schemed with Teva, a generic manufacturer, to prevent other generic versions of Effexor XR from reaching store shelves for at least two years after its exclusive marketing rights to the drug expired in June 2008. The suit claims Wyeth accomplished this by obtaining fraudulent patents, engaging in fake litigation with Teva and other generic manufacturers, and scheming to prolong Teva’s generic exclusivity rights. As a result, the retailers claim they were overcharged.

CVS and Rite Aid seek treble damages and other remedies.