PARSIPPANY, N.J. — In what it called the largest generic product launch in U.S. history, Watson Pharmaceuticals Inc. has begun shipping an authorized generic version of Pfizer’s blockbuster cholesterol-lowering drug Lipitor.

The shipment of Watson’s Lipitor generic signals the start of the "generic wave."

Watson said Wednesday that it is rolling out the product, atorvastatin calcium tablets, as part of an exclusive agreement with Pfizer Inc.

Under the terms of the supply and distribution agreement, Pfizer manufactures and supplies Watson with all dosage strengths of the authorized generic product. Watson markets and distributes the product in the United States.

Meanwhile, Pfizer will receive a share of the net sales from Watson’s sales of the product. The agreement runs until Nov. 30, 2016, according to Watson. Other terms of the agreement haven’t been disclosed.

Lipitor had sales of about $7.8 billion for the most recent 12 months ended Sept. 30, according to IMS Health figures reported by Watson.

Lipitor is indicated as an adjunct to diet to reduce elevated total cholesterol, LDL cholesterol and triglycerides as well as to increase HDL cholesterol.

The inception of a Lipitor generic signals the start of the so-called "generic wave" or "patent cliff," in which roughly a dozen blockbuster prescription drugs in the United States will lose patent protection over the next two years.