The US pharmaceuticals giant Merck has predicted that its earnings in 2002 will be little changed on those for this year.

The company says it will be hit by the expiration of patents on key drugs, and slower sales growth for its key arthritis drug Vioxx.

The announcement surprised analysts and sent its share price sharply downwards on Wall Street.

"We anticipate earnings per share at the same level as 2001," said the company's chief financial officer Judy Lewent.

"This 2002 guidance is not at the level that we would have liked to deliver."

Surprise

Merck's share price slumped 9.4% to close at $60.70.

The news also cast a shadow across the rest of the market, reversing earlier gains and pushing the Dow Jones index back below the 10,000 level.

Analysts said they had been expecting some slowdown in growth next year, but said the news from Merck was far worse than they had been expecting.

Merck faces the loss of patents on some of its top medicines next year in the US, including hypertension treatment Prinivil and ulcer medicine Prilosec.