Several generic drugmakers have launched cheap copies of AstraZeneca's top-selling heartburn and ulcer treatment Nexium in Germany.

A spokesman said on Friday the Anglo-Swedish company was aware that copycat versions of Nexium had arrived on the market, adding such generic competition had been anticipated in certain European countries during 2010.

Nexium was always expected to face earlier generic competition in Europe than in the United States, its most important market, with the timing of European launches varying from country to country.

In the United States, cheap copies of Nexium, or esomeprazole, are not expected until 2014, following settlement deals struck between AstraZeneca and generics firms.

AstraZeneca gave no details on how many versions of generic Nexium had been launched in Germany but one industry source said products from four manufacturers had now reached the market.

German generics group Ratiopharm, now part of Teva Pharmaceutical Industries, said a month ago that it expected to launch its version of the drug in Germany during September at a discount of more than 60 percent to the original product.

Nexium was AstraZeneca's biggest-selling drug in 2009, with global sales of $5 billion -- but its importance is declining. It was eclipsed this year by cholesterol fighter Crestor, which is now AstraZeneca's most important product. - Reuters