Preferred position on the formulary typically means the preferred drug must be tried first, or has a lower co-payment.

But recently pharmacy benefit managers have been trying a more powerful weapon to increase their bargaining leverage — refusing to pay at all for the less preferred drug. Express Scripts’ national preferred formulary, which is used by many employers and covers 25 million people, will exclude about 70 drugs next year, including Harvoni, Sovaldi and another new hepatitis C drug, Johnson & Johnson’s Olysio.

Gilead, in a statement, said it had “been negotiating in good faith with Express Scripts and other payers” and hoped to continue to have discussions “that focus on the best interests of patients with hepatitis C.” A company spokeswoman declined to say what fraction of Gilead’s hepatitis C sales were covered by Express Scripts.

Doctors who treat hepatitis C cheered the fact that all patients would be treated, regardless of the severity of their disease.

“It’s going to expedite treatment for patients,” said Dr. Rena Fox, a hepatitis specialist at the University of California, San Francisco. “It certainly avoids putting doctors in a very uncomfortable position of having to say yes to some patients and no to other patients.” Dr. Fox said that any differences between AbbVie’s and Gilead’s drugs were minor, so there was no problem in excluding Gilead’s drugs.

But Dr. Eugene Schiff, director of the center for liver diseases at the University of Miami, disagreed. He said Harvoni was one pill once a day while AbbVie’s drug required four pills, three in the morning and one in the afternoon. And many patients getting Viekira also have to take ribavirin, an older drug that can have serious side effects.

“To say that it’s exclusively this drug is not right,” Dr. Schiff said.

Harvoni and Viekira Pak are approved only for so-called genotype 1 hepatitis C, which accounts for about 70 percent of cases in the United States. Express Scripts said it would still pay for Sovaldi when used to treat other genotypes. And patients already taking Sovaldi or Harvoni can continue.