Pfizer will allow Teva to sell generic Viagra Tue Dec 17, 2013 1:40pm EST (Reuters) - Pfizer Inc on Tuesday said it would allow Teva Pharmaceutical Industries to sell generic forms of its Viagra anti-impotence treatment in the United States beginning in late 2017, in a settlement of longstanding patent litigation between the two drugmakers. Pfizer's U.S. patent on Viagra lapses in 2020, including a six-month extension granted for having tested the medicine in young patients. That means Israeli drugmaker Teva, under the arrangement, could launch its generic version several years before other generic drugmakers. Pfizer said in a statement that it would receive a royalty from Teva, but no other financial details were disclosed. Teva will be authorized to launch its U.S. generics by December 11, 2017, or earlier in certain circumstances. Viagra began facing cheaper generics in Europe in June, including formulations sold by Teva. Viagra, the first drug to treat impotence, was approved by U.S. regulators in 1998. It has annual sales of about $1.8 billion, including U.S. sales of $1.2 billion. Pfizer's basic U.S. patent on Viagra had been slated to lapse in 2012, which would have opened the floodgates to cheaper generics. But a federal judge in Norfolk, Virginia, in 2011 - during the legal battle with Teva - ruled that a secondary Pfizer patent covering the way that Viagra is used protects the oral drug from generic competition well into 2019. Pfizer shares were little changed in afternoon trading on the New York Stock Exchange. Reporting by Ransdell Pierson; Editing by Leslie Adler