TRENTON, N.J. -- A federal court invalidated the patent yesterday for
The company also was hit with news that the federal Securities and Exchange Commission is starting a formal inquiry into Merck's handling of arthritis blockbuster Vioxx, which it withdrew from the market last year after studies showed it increased the risk of heart attacks and strokes.
Merck's shares tumbled $3.16, or 10.1 percent, to $28.02 on the New York Stock Exchange. More than 57 million shares were traded, or roughly six times normal daily volume for Merck.
The US Court of Appeals for the Federal Circuit in Washington invalidated the patent for the once-a-week version of Fosamax. More than 3 million people in the United States afflicted with the brittle-bone disease take Fosamax.
Under the ruling, generic competition could begin as soon as early 2008, instead of 2018.
Fosamax is the number two drug for Whitehouse Station, N.J.-based Merck. It reported sales of $3.16 billion for Fosamax last year, a company spokesman said.
The company's leading drug is Zocor, which is for high cholesterol.