Kasowitz, Benson, Torres & Friedman has sued its long-time client Duane Reade Inc. for a $7 million “success fee” it claims it is owed as part of an alternative fee arrangement. (See the complaint.)

The Manhattan-based law firm represented Duane Reade in a contract dispute with Cardtronics LP, an ATM operator. But when the drug store chain switched general counsel in 2008, it settled the dispute for an estimated $39.5 million without the law firm’s knowledge. Kasowitz claims in court papers that the settlement included terms negotiated by the firm during the course of the litigation, and that it is owed a 20 percent share of the settlement under its alternative fee agreement.