Pfizer Inc. said Thursday that a federal appeals court has overturned a lower court decision that upheld the patent protecting its widely-prescribed hypertension drug Novasc, a move that opens the door to early generic competition.

In a statement, Pfizer said the U.S. Court of Appeals for the Federal Circuit reversed a lower court ruling in favor of Pfizer, which found the Norvasc patent to be valid and enforceable. The appeal was brought by Apotex, which has been seeking to have the Pfizer patent nullified in order to put out a generic version of the drug.

Pfizer added that it is "reviewing the decision and is considering all its options, including seeking reconsideration."
Other generic drugmakers have also been seeking to put out generic versions of the drug, including Mylan Laboratories (MYL) . Norvasc is slated to lose patent protection later this year.

Prudential analyst Timothy Anderson said in his note Thursday that the appeals ruling could allow for the introduction of generic versions of Norvasc as soon as next week.

"We did not anticipate this ruling, but it will probably only have a muted impact on Pfizer which is already a washed-out, low valuation name," wrote Anderson.

"Earlier generic entry is a negative and could cost the company $1 billion in sales or so in 2007, but given Pfizer's size and cash generation this it not very material to the company's future outlook, in our opinion," Anderson added.