Copycat versions of Pfizer’s cholesterol-lowerer Lipitor have begun shipping in Canada as the world’s biggest drugmaker faces up to the loss of patent protection in North America for the world’s best-selling drug.

The first company to show its hand was Canada’s own Apotex which heralded the arrival of its version of Lipitor (atorvastatin). The Toronto-headquartered firm said that the last patent on Pfizer’s drug will not expire until 2022 so to overcome this, the firm has invented its own crystal form, “a 100% Canadian-made product” called Apo-Atorvastatin.

Bringing a generic to market 12 years ahead of time “will result in close to $7 billion of cost-savings for the Canadian healthcare system,” Apotex said, and chief operating officer Jack Kay claimed that “this is a historical moment as provincial governments are struggling with increasing deficits”. Apotex spent “many years and many millions of dollars on the development and litigation processes for this product,” and Mr Kay claimed that “the risks for companies like ours to develop products and to litigate are huge, but the real beneficiaries are the public and private payers and consumers”.

Apotex’ announcement was swiftly followed by Teva Pharmaceutical Industries and Watson Pharmaceuticals saying that they would be shipping their versions of Lipitor The drug had total Canadian sales of approximately $1 billion for the year ending March 2010, according to IMS Health figures, and Watson chief executive Paul Bisaro noted that it is “the largest product to be offered as a generic in the history of the Canadian generic pharmaceutical industry”.

As for Pfizer, spokeswoman Sally Beatty told Reuters that the company would not be surprised if a half-dozen Lipitor generics end up on the Canadian market. However, “we'll be offering alternative versions of atorvastatin” too, she added, though she declined to give any timeline for an authorised generic or how much it would cost.

Ms Beatty also noted that Lipitor's market exclusivity in Canada actually lapses on July 19 but stated that Apotex and Pfizer reached an agreement two years ago to permit an earlier launch. While the loss of sales will hurt the drugs giant, things will get worse in November 2011, when Pfizer loses US marketing exclusivity on Lipitor, which currently brings in around $12 billion worldwide.