Lipitor (atorvastatin), Zocor (simvastatin), Crestor (rosuvastatin), and other statins can dramatically lower levels of artery-clogging cholesterol in the blood, an ability that makes them hugely popular in our cholesterol-rich country. Heart researchers have estimated that these drugs could save 1,000 lives each week for every 10 million high-risk heart disease patients who take them.

One study of nearly 20,000 patients found that, after a heart attack, taking a statin can prevent the risk of death within one year by 25%. Among patients who don't even have cardiovascular disease, taking a statin preventively can reduce the risk of a major coronary event like heart attack by about 30%.

When Denise Foley, 57, of Philadelphia, went through menopause, her cholesterol shot up from 160 to 240. Her doctor warned her that that number, along with her family history of heart disease, put her at risk for a heart attack or stroke. But she didn't want to take heart medication. "I really wanted to lower my risk without drugs," she says. "I lost 30 pounds, I exercised, and I went on a vegetarian diet. But I just couldn't budge it."

Seven years ago she was prescribed Lipitor to control her high cholesterol. Soon after, she started feeling depressed for no reason. "I went to a party filled with good friends, and I sat in the corner and thought everyone hated me," she says. Turns out depression can be a side effect of Lipitor. Her doctor switched her to Zocor, which she now takes successfully. Her cholesterol is in a safe range. "I worry about the long-term effects of these drugs," she says. "But I also know that without medication, I might be dead from a heart attack or stroke."

As of December 2006, an estimated 13.1 million Americans had a prescription for a statin, an increase of 500,000 patients in just over a year. In 2004, Americans spent more than $9 billion on Lipitor alone, more than for any other prescription drug. The arrival in 2006 of two inexpensive generic statins—pravastatin and simvastatin—will make statins available to even more patients.

Statins lower cholesterol in two ways: They encourage the liver to clear LDL (bad cholesterol) from the blood, and they block an enzyme that the body needs to make new cholesterol.

At high doses, statins can nudge up your HDL (good cholesterol) while lowering your LDL (bad cholesterol) by 50% or more. Studies have shown that, for patients who already have heart disease, taking a statin can reduce the risk of fatal coronary events within five years by up to 40%. According to Thomas H. Lee, a cardiologist and editor in chief of the Harvard Heart Letter, even people who don't have high cholesterol can cut their risk of heart disease by a third simply by taking a statin.

More on heart drugs

Even given their wild popularity, "statins are still underprescribed," says Thomas Allison, PhD, a cardiovascular specialist at the Mayo Clinic in Rochester, Minn. "The drugs could do much more good if more people took them to prevent heart disease, not just treat it," he says. "Most people aren't receiving cholesterol treatment until they've had a heart attack."

Joe Marzan, 32, a heart attack survivor in Prineville, Ore., was given a preventive prescription for statins because he had high cholesterol and a fatty diet, and because his father had had coronary bypass surgery. "I didn't take it regularly, though," he says, because he thought he was too young to worry about heart disease.

When a checkup showed that his total cholesterol had climbed to an incredible 400, his doctor urged him to come in for more aggressive treatment, including higher doses of Zocor or Lipitor. But Marzan, who has two kids, was in the process of moving to a new town and put off the appointment. His heart attack struck seven months later. Now he counsels other heart disease patients on the importance of compliance. "If I had listened to my doctor, I might have dodged this bullet," he says.

Statins generally don't cause many side effects, but potentially the most common problem is muscle pain, stiffness, or weakness, which affects about 1% of study subjects but many more patients in the real world, because study subjects are carefully screened, says Eliot Brinton, MD, a preventive cardiologist and lipidologist at the University of Utah School of Medicine. Other side effects can include tiredness, bloating, constipation, and leg and abdominal pain. More serious side effects—including liver damage—are rare. Roughly one out of six million patients taking Lipitor has a fatal reaction. "Walking down to the store to get the drug is more dangerous than taking it," Allison says.

Some experts have expressed concern that the emphasis on statins could draw attention away from the importance of diet and lifestyle. A 2007 study of 71 patients who began taking statins found that 44% felt their physician had prescribed the statin even though the patients preferred to try dietary measures to control their cholesterol. And although 76% of the patients wanted to reduce their dietary fat intake when they began statin treatment, after six months there was no significant change in the group's fat intake.

But the biggest risk with statins is not taking them. Only about half of all patients prescribed a statin end up reaching their cholesterol goals, mainly because far too many people leave far too many pills untouched.

One recent study of nearly 6,500 patients found that they refilled their monthly prescriptions an average of less than five times a year.