Pharmaceutical company Actavis said on Tuesday that it would once again sell a generic version of Bayer's Yaz after an appeals court ruled that Bayer's patent for the oral contraceptive was invalid.

The U.S. Court of Appeals for the Federal Circuit ruled on Tuesday that a U.S. District Court in Nevada erred last March in finding the patent to be valid. It reversed the ruling.

Actavis had launched its generic competitor in January 2012, but took it off pharmacists' shelves after the ruling in Nevada.

The generic companies involved in the ruling -- Watson Pharmaceuticals, which now goes by the name Actavis; Sandoz, which is the generic drug unit of Novartis ; and Lupin -- had argued that the patent was invalid and had told the U.S. Food and Drug Administration that they planned to sell generic versions of the contraceptive.

Sandoz will continue to ship its generic version of Yaz, which it began selling in 2011, a company spokeswoman said. Lupin declined to comment on the decision.

The challenged patent expires on June 30, 2014, the ruling said.

"We disagree with the court's ruling and are evaluating our options," Bayer spokeswoman Astrid Kranz said in an email.

Global sales of Bayer's Yasmin and Yaz birth control pills, which total more than $1 billion annually, have been on the wane because of potential side effects and competition from cheaper generics.

Yaz is a reformulated version of Yasmin and remains one of the top-selling contraceptives in the United States. Actavis said that U.S. sales of Yaz, both branded and generic, were about $347 million annually.

Bayer's Yasmin brand has been controversial. In 2012, Bayer agreed to pay a combined $400 million to settle almost one third of about 6,000 legal claims in the United States that Yasmin caused blood clots.

In April 2012, the FDA added information to the labels on Bayer's Yaz and Yasmin, as well as others, to show they may raise the risk of blood clots.

All common birth control pills increase the chances of potentially fatal blood clots, but the FDA said the danger may be greater for more recent pills that contain the synthetic hormone drospirenone.

The cases at the Federal Circuit are: Bayer Healthcare Pharmaceuticals, Inc. v. Watson Pharmaceuticals Inc. and Sandoz Inc. (Case Nos. are 2012-1397, -1398, -1400) and Bayer Schering Pharma AG v. Watson Pharma and Lupin, Ltd. (Case No. 2012-1424.)