In dealing with health plans, drug companies are facing a new imperative — bargain or be banned.

Determined to slow the rapid rise in drug prices, more health plans are refusing to cover certain drugs unless the companies charge less for them.

The strategy appears to be getting pharmaceutical makers to compete on price. Some big-selling products, like the respiratory medicine Advair and the diabetes drug Victoza, have suffered precipitous declines in market share because Express Scripts, the biggest pharmacy benefits manager, recently stopped paying for them for many patients.

“There’s clearly more price competition in the marketplace,” Andrew Witty, chief executive of GlaxoSmithKline, said, talking about Advair in a recent company earnings call.

Executives of pharmacy benefit management firms say they must do something to cope with rising prices, particularly for so-called specialty pharmaceuticals, which are used to treat complex diseases like cancer and multiple sclerosis.