Overuse and underuse of cholesterol-lowering drugs called statins may be widespread, risking side effects in some people and failing to stop heart disease in others, researchers report.

Of more than 29,000 primary care patients drawn from Boston's Brigham and Women's Hospital and associated sites, 1,575 were receiving statins during 1996, according to the report in the January 8th issue of Archives of Internal Medicine. These included patients with heart disease as well as 1,080 without documented disease who were taking the medication as "primary" preventive therapy.

Fewer than one in three people taking the drugs to prevent heart disease met National Cholesterol Education Program guidelines for who should take the drugs, the study authors write.

What's more, about half of the more than 500 individuals who wer e receiving statin therapy because of known heart disease met the guidelines, meaning that 47% of that group were being overtreated.

The researchers also evaluated another 1,459 patients who had coronary heart disease (CHD) but were not on statin medications. The investigators found that "88% met the criteria for being able to receive a statin, and were thus undertreated."

A number of factors could explain the results, according to Dr. Susan Abookire, the Harvard-affiliated lead researcher, from Partners Healthcare in Boston, Massachusetts.

Doctors may not follow treatment guidelines or keep up with current research on statins, she said. And to be on the safe side, some physicians may prescribe more medication rather than less.

"They're also influenced by what their patients want, which is influenced by advertising," Abookire added. In the study, patients most likely to be overmedicated were those at least 70 years old, those without risk factors, or those who had fewer than two risk factors for heart disease.

Research has shown that people with elevated low-density lipoprotein, or "bad" cholesterol, can reduce their risk of dying from the disease by taking statins. So can people who already have heart problems.

However, statins themselves are not risk-free. Depending on the specific statin, side effects may include:

Periodic testing to monitor liver function should be performed.

Statin underuse means some deaths or "at least some adverse outcomes" could possibly be prevented, Abookire said.

Her team's research did not try to determine the number of preventable deaths or poor patient outcomes due to statin misuse. But it did estimate that more than $1.3 million might have been saved if patients with or without heart disease had been medicated according to the guidelines.

Archives of Internal Medicine 2001;161:53-58