The health and welfare fund of the Philadelphia Federation of Teachers filed a lawsuit against Merck & Co. Inc. and Schering-Plough Corp. over what the fund says were excessive charges for Vytorin used by its members.

Vytorin, a cholesterol drug, is marketed by the two pharmaceutical companies.

The suit, seeking $3 million, accuses the companies of false advertising to create a demand for Vytorin, which cost substantially more than other medications "but was of questionable additional benefit," the fund said in a statement.

A spokeswoman at Schering-Plough, of Kenilworth, N.J., said the company stands behind its products, has done nothing wrong, and will defend the lawsuit vigorously.

A study in January showed that Vytorin was no better at reducing plaque buildup in neck arteries than Merck's Zocor, one of Vytorin's ingredients, which is available in a cheaper generic form. Vytorin's second ingredient is Schering-Plough's Zetia.

Another study released this week by European researchers also reported disappointing results for Vytorin, whose list price is $100 for a month's supply.

The suit was filed Monday in Common Pleas Court in Philadelphia.