The world's most popular blood pressure medicine, hydrochlorothiazide, is much less effective than comparable drugs and gives patients a false sense of security, researchers said.
In a review of earlier studies, they found the diuretic lowered blood pressure by only about half as much as common alternatives such as beta blockers and ACE inhibitors.
High blood pressure affects about a third of US adults, according to the National Heart, Lung, and Blood Institute (NHLBI), and ups the risk of heart attack and stroke when left unchecked.
"By giving hydrochlorothiazide we give patients and physicians a false sense of security," said study researcher Dr Franz Messerli, who heads the hypertension program at St. Luke's-Roosevelt Hospital in New York.
Not to be used
"Hydrochlorothiazide should no longer be used alone," he urged, adding that he has been prescribing it to patients himself for the past 25 years.
The NHLBI currently recommends thiazides as first-line treatment to rein in high blood pressure, after a large government-funded study failed to find additional benefits from newer, more expensive medicines.
The problem is that hydrochlorothiazide, which wasn't tested in that study, remains the go-to water pill, said Dr Messerli.
According to his report, published in the Journal of the American College of Cardiology , American doctors wrote 134 million prescriptions for the drug in 2008 alone, landing it far ahead of the beta-blocker atenolol, the second-most commonly used blood pressure medicine.
"You cannot just recommend a thiazide as the NHLBI does, knowing that for physicians that translates into hydrochlorothiazide," Dr Messerli said. Neither the NHLBI nor the American Heart Association could be reached for comments.
For the new study, Dr Messerli and colleagues reviewed 19 studies that compared hydrochlorothiazide to other drugs in randomised trials.
Measured over 24 hours, the low doses of hydrochlorothiazide commonly used reduced systolic blood pressure by 6.5 points.
In contrast, angiotensin-converting enzyme (ACE) inhibitors cut systolic blood pressure by 12.9 points, beta blockers by 11.2 points, and calcium-channel blockers by 11 points.
While higher doses of hydrochlorothiazide were more effective, Dr Messerli said they were rarely used because of an increase in side effects such as blood sugar and insulin problems.
He added that office-based blood pressure measurements could be deceiving, because hydrochlorothiazide appears to be particularly weak during the night.
"We know that night time blood pressure and early-morning blood pressure are very important risk factors for strokes and heart attacks," Dr Messerli said, although he added that how hydrochlorothiazide affects those risks has never been studied.
The new findings don't concern other thiazides such as chlorthalidone or indapamide.(Reuters Health/ January 2011)
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