DALLAS -- Women taking daily amounts of nonaspirin painkillers -- such as Extra Strength Tylenol -- are more likely to develop high blood pressure than those who don't, a new study suggests.
Researchers from Harvard University and Brigham and Women's Hospital reported yesterday in the medical journal Hypertension that taking 500 milligrams or more of a nonaspirin painkiller doubled the risk of having high blood pressure. The findings were based on detailed questionnaires submitted by nurses about their health.
One of the authors of the study, Dr. Gary Curhan, said it was too soon to recommend that federal regulators slap warnings on boxes of nonaspirin painkillers alerting consumers to a potential blood-pressure risk. Instead, he said, further studies of the possible danger should be conducted.
Still, Curhan said, the findings contain an important message for patients.
''Commonly used medications available over the counter at a drugstore may have adverse effects as well as beneficial effects," said Curhan, an associate professor at Harvard Medical School.
The researchers, whose study was released yesterday, first reported on a possible link between painkillers and high blood pressure in 2002.
Federal regulators earlier this year required that another class of pain relievers, nonsteroidal anti-inflammatory drugs, carry warning labels because of the risk of heart problems. Those include ibuprofen, sold as Advil and Motrin, and naproxen, sold as Aleve. Many had turned to those painkillers following problems with prescription drugs, such as Vioxx.
The new study also found that those nonsteroidal anti-inflammatories -- commonly known as NSAIDs -- appeared to increase blood pressure. Aspirin did not appear to pose a problem.
''If you're taking these over-the-counter medications at high dosages on a regular basis, make sure that you report it to your doctor and you're checking your blood pressure," said Dr. Christie Ballantyne, a cardiologist at the Methodist DeBakey Heart Center in Houston who had no role in the study.
The research found that aspirin remains the safest medicine for pain relief. It has long been known to reduce the risk of cardiovascular problems and was not included in the government's requirement for stricter labels for NSAIDs.
The study involved 5,123 women participating in the Nurses Health Study at Harvard Medical School and Brigham and Women's. None had high blood pressure when it began.
''It certainly sets the basis for more studies," said Dr. Stephanie Lawhorn, a cardiologist at St. Luke's Mid America Heart Institute in Kansas City.
The study found that women ages 51-77 who took an average daily dose of more than 500 milligrams of acetaminophen -- one Extra Strength Tylenol -- had about double the risk of developing high blood pressure within about three years. Women in that age range who take more than 400 milligrams per day of NSAIDs -- equal to about two ibuprofen -- had a 78 percent increased risk of developing high blood pressure over those who didn't take the drug.
Women 34-53 who took an average of more than 500 milligrams of acetaminophen per day during the study had a twofold risk of developing high blood pressure. And those who took more than 400 milligrams of NSAIDs per day had a 60 percent risk increase over those who didn't take the pills.
''We are by no means suggesting that women with chronic pain conditions not receive treatment for their pain," lead author Dr. John Phillip Forman, of Harvard Medical School and associate physician at Brigham and Women's, said in an e-mail.
Previous research linking these drugs to blood pressure problems did not look at dose.
As for why aspirin didn't raise risk, it might be because ''aspirin has a different effect on blood vessels than NSAIDs and acetaminophen have," said Dr. Daniel Jones, dean of the school of medicine at University of Mississippi Medical Center in Jackson.
Stephen Smith of the Globe staff contributed to this report.