Water Pills Help All With Hypertension

If you're not taking a diuretic for high blood pressure, experts say you should ask your doctor about switching medications.

Medically Reviewed by Charlotte E. Grayson Mathis, MD on January 02, 2003
4 min read

The largest hypertension study ever conducted has found that the simple "water pill" is preferred to newer, more popular and expensive drugs and should be the designated choice "for use in starting treatment for high blood pressure."

But what if you're among the 24 million Americans taking other types medications to manage hypertension? Should you talk to your doctor of switching to a diuretic (water pill), whose use has dwindled in recent decades with the introduction of newer drugs?

"Yes," says the lead researcher of this landmark study, called ALLHAT for the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial.

"The bottom line of our study is that diuretics should be considered as the first step for treating all new cases of hypertension," Barry R. Davis, MD, PhD, of the University of Texas School of Public Health, tells WebMD. "But diuretics should also be part of every hypertensive regimen."

Davis adds that while the study findings recommend using diuretics to start treatment of high blood pressure, it shouldn't be interpreted to suggest that only newly diagnosed patients would benefit from them.

"The way the clinical trail was conducted, 90% of the study participants had been on some type of medication [before the study], and their medication was stopped and they were switched to four different drugs in randomized fashion -- including the diuretic," he says. "And those taking the diuretics, which are much less expensive, fared as good or better."

Plus, they don't cause any additional side effects than the other drugs -- typically increased urination that subsides after several weeks, and sometimes dizziness, muscle weakness, and cramps. "In rare cases, someone can't take them because they may be allergic to them," says Davis. "But for the average patient, they are the better choice. So if you are on another medication and your blood pressure is not controlled, and another medication has to be added, as is often the case, it should be a diuretic."

The results of the eight-year ALLHAT trial, released recently in the Journal of the American Medical Association, brings new attention to this old standard in blood pressure treatment, which works by ridding the body of excess salt and water. The generic diuretic used in the study, chlorthalidone, was deemed a better choice than two other types of treatments that can cost as much as 30 times more --- the ACE inhibitors Prinivil or Zestril and the calcium channel blocker Norvasc. A third medication, the alpha-blocker Cardura, was dropped from the study some two years ago because it increased the risk of heart disease and stroke in study participants.

The diuretic was found to be better at lowering systolic blood pressure -- the top number in a blood pressure reading -- than the newer drugs, but Norvasc was more effective in reducing diastolic blood pressure, the bottom number. However, those taking Norvasc had a 38% higher risk of developing heart failure and a 35% higher chance of being hospitalized for the condition. Meanwhile, those on the ACE inhibitor had a 15% higher risk of stroke, a 19% higher risk of developing heart failure, and other increased risks compared with people taking a diuretic.

And then there's the cost factor: While diuretics cost between 6 cents and 10 cents a day, it costs about $1.60 daily for a beta-blocker (another drug used to treat high blood pressure) and $1.46 for an ACE inhibitor. There are various types of diuretics for hypertension management, but the most popular is hydrochlorothiazide, or HCTZ, which has fewer side effects than the type used in the ALLHAT study. HCTZ is often combined with other diuretics into one pill.

So why have diuretics dropped in popularity in recent years? In 1982, diuretics represented 56% of all prescriptions written for high blood pressure; ten years later, they comprised only 27% of those prescriptions.

"Physicians have changed their practice [in prescribing other medications], based on the assumption that if it's newer, it probably is better, says Paul K. Whelton, MD, MSc, of Tulane University School of Public Health and Tropical Medicine, another researcher on the study. "But the use of diuretics has certainly been the recommendation from every national body that has offered treatment guidelines.

"What this finding does is provide a definitive answer to the question of what medication is best," Whelton tells WebMD. "Now, there is strong scientific evidence that there is clearly no additional benefit from newer agents that are more expensive. And when you look at evidence of important clinical indicators -- namely heart failure and stroke, diuretics perform better."

But switching from newer drugs to a diuretic, the study researchers say, would save between $250 and $650 per patient per year. So is the medical community bracing for a change in the way high blood medications are prescribed?

"This study will lead physicians to rethink how they treat high blood pressure," says Daniel Jones, MD, of the American Heart Association, in a prepared statement. "But we strongly urge patients to continue taking their current medication until they have talked with their physician to determine the best treatment."

Meanwhile, a spokesman for the American Medical Association says that the governing body of practicing physicians -- which publishes the medical journal in which the study appeared -- "has not yet reviewed the study and therefore cannot make a recommendation."