Patent on Claritin Is Ruled Invalid

Schering-Plough Corp. lost a legal battle with generic-drug makers when a U.S. judge ruled that a patent on its top-selling Claritin allergy drug was invalid.

Unless overturned on appeal, the ruling would clear the way for generic-drug makers to start selling versions of Claritin in December.

The drug had almost $3.16 billion in worldwide sales last year, almost a third of the Kenilworth, N.J.-based company’s total.

Schering-Plough shares, which declined as much as 11% after the ruling, fell $1.30, or 5%, to $22.88 on the NYSE.