WASHINGTON — A $1,000-per-pill drug that insurers are reluctant to pay for has quickly become the treatment of choice for a liver-wasting viral disease that affects more than 3 million Americans.

In less than six months, prescriptions for Sovaldi have eclipsed all other hepatitis C pills combined, according to new data from IMS Health. The prospect of a real cure, with fewer nasty side effects, is enticing thousands of patients to get treated for the first time.

But clinical and commercial successes have triggered scrutiny for the drug’s manufacturer, California-based Gilead Sciences, which just reported second-quarter profits of $3.66 billion, a net margin of 56 percent.

Two senior senators are raising questions about documents that suggest the initial developers of Sovaldi considered pricing treatment at less than half as much. The health insurance industry is publicly scolding Gilead, and state Medicaid programs are pushing back.

The repercussions for patients could go beyond one drug and one disease.

A number of promising cancer medications near approval could provide the next storm over costs. The average cost of brand-name cancer drugs has doubled in a decade, to about $10,000 a month.

“You can’t put too fine a point on the sort of moral dilemma that we have here,” said Michael Kleinrock, director of the IMS Institute, which studies prescription drug trends. “This is something that the research-based pharmaceutical industry reaches for all the time: a cure. But when they achieve one, can we afford it?”

New data from IMS Health, the Connecticut parent company of the institute, illustrate Sovaldi’s impact since its debut December:

n The total number of pharmacy prescriptions for all hepatitis C pills has soared. In May, more than 48,000 prescriptions were filled for four such medications, with Sovaldi accounting for three-fourths of the total. By comparison, prescriptions for May 2013 totaled about 6,200. That was before Sovaldi became available.

n In Sovaldi’s first 30 weeks on the market, 62,000 new patients tried it, nearly three times as many as had tried an earlier medication that showed initial promise. That makes Sovaldi the most successful launch for any hepatitis C drug. And Gilead expects to have a successor soon that will make treatment easier to tolerate.