Analysts said the approval would potentially usher in greater competition and lower prices for this critical class of drugs.

“The biological products tend to be products that have very high prices,” Dr. John K. Jenkins, director of the Office of New Drugs in F.D.A.’s Center for Drug Evaluation and Research, said on a call with reporters. “With competition, one of the goals is to see hopefully lower prices to make access better for the patients who need these products.”

Biosimilars are about a third cheaper than brand-name biologic drugs, on average, in countries where they are in use, according to Express Scripts, the nation’s largest manager of prescription drug benefits. Some experts say the discounts could be much steeper, up to 90 percent.

Express Scripts estimates that Zarxio’s introduction in the United States could save $5.7 billion in drug costs over the next 10 years. It estimated that $250 billion in drug costs could be saved over the next decade if 11 biosimilars in development were approved.

A spokeswoman for Novartis, Elizabeth Power, declined to comment on Zarxio’s price.

Amgen, the maker of Neupogen, has gone to court trying to block the sale of Zarxio. It says Sandoz did not follow the rules in terms of informing Amgen in advance of its plans for the drug. Sandoz has denied that. A hearing is scheduled for March 13 on Amgen’s request for a preliminary injunction. Sandoz said it would not start selling Zarxio until a decision was made on the injunction or April 10, whichever came first.

The F.D.A. approved Zarxio for all the uses of its predecessor, Neupogen, and allowed the drug to carry nearly identical language on its label. That suggests that biosimilars as a share of the market may grow quickly, said Mr. Gal, the pharmaceuticals analyst, as they will be allowed to be used as broadly as the drugs they imitate.

“We did not see any differences that would suggest that there would be any situations where a prescriber would have to choose one or the other based on safety and efficacy,” Dr. Jenkins said. “They should perform the same.”