For the estimated tens of millions of Americans at risk for heart disease, Pfizer’s announcement that it has ended its trials of torcetrapib is doubly disappointing. Not only has a highly publicized treatment been proven too dangerous, but similar drugs being from other companies will face greater scrutiny — and delays — in getting to market.

Statins like Lipitor and Zocar, which have been on the market for 20 years, have been shown to reduce low-density lipoproteins — the so-called bad cholesterol — that form plaque on the walls of arteries, inhibiting blood flow and increasing the risk of a heart attack. While useful for millions of Americans, statins only reduce cardiovascular event rates by about one-third.

“The most important thing to understand is that we have got to get beyond the limits of what we can do with statin drugs,” said Dr. Steven E. Nissen, chairman of cardiovascular medicine at the Cleveland Clinic and lead investigator of an earlier torcetrapib clinical trial. “They work great, but if we put statins in the water supply, cardiovascular disease would still be the leading cause of death in most Western countries.”

The next great leap in treatment was to be drugs like torcetrapib that would also increase high-density lipoproteins — the so-called good cholesterol — by more than 30 percent. Good cholesterol makes it more difficult for bad cholesterol to form plaque, which is why doctors typically express a patient’s cholesterol risk as a ratio of total cholesterol to good. (Statins also increase good cholesterol, but only by about 5 percent.)

Because it still hasn’t been determined what caused the health problems in the torcetrapib study, similar drugs will come under intense scrutiny. Roche, the Swiss pharmaceutical company, is developing a good cholestoral drug that is scheduled to enter the final phase of study before approval, called phase three trials. Industry analysts said last night that the Food and Drug Administration would likely now require lengthy outcome trials, spanning between three and five years.

There is one currently available drug that raises good cholesterol: Niaspan, a drug sold by Kos, a company that is being acquired by Abbott Laboratories. However, Niaspan can increase good cholesterol by only about 14 percent for men and 20 percent for women and often causes hot-flashes. Merck has two similar medications, known as 524 drugs, in phase two trials that the company says will eliminate the hot flash side effect.

But analysts said the failure of torcetrapib does not mean that drug companies will stop pursuing improved cholesterol drugs.

“There’s really a genuine interest by drug companies, the patients, the doctors, and the medical community about raising good cholesterol, so one way or another the drug companies will probably find a good way to do that,” said Michael Krensavage, the drug analyst at Raymond James, a financial services firm. “It just looks like torcetrapib isn’t the one. But it isn’t over in terms of good cholesterol.”