SHARES in Merck, the American drugs giant, slipped 1.2 per cent in early trading on Wall Street yesterday amid reports that class action lawyers were targeting a second blockbuster drug at the company.

Lawyers filed a suit in the District Court of Fort Myers alleging that Merck had marketed a treatment for osteoporosis, called Fosamax, despite knowing that the medicine might have links to a rare disease that causes the patient’s jaw bone to rot and die.

The action builds on a similar case last autumn when a firm in Knoxville, Tennessee, filed a similar suit against the American drugs giant.

The news comes a day after a jury in Atlantic City ordered the company to pay $9 million (£5.1 million) in damages to a man who had suffered a heart attack after taking Vioxx, a painkiller. The jury ruled that Merck had misled US drug regulators about the dangers of the medicine and that it had acted with “wanton disregard” for patients taking the medicine.

Dentists began to notice a link between patients taking the family of drugs to which Fosamax belongs and osteonecrosis, or bone decay, of the jaw as early as 2001.

They originally thought that the problem was limited to cancer sufferers taking a highly potent version of the medicine to stop tumours from eating away at healthy bone material.

Class action lawyers will try to prove that Merck engaged in the same aggressive marketing techniques for Fosamax as it did for Vioxx. The drug currently generates more than $3 billion in revenues a year.

In a statment, Merck said that the cause of oseteonecrosis of the jaw was still not fully understood. It added that it had inserted two paragraphs of extra precaustions in prescribing informartion for doctors in July 2005 after discussions with the US drug regulator.

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