Adding Diuretic to Drug Regimen Lowers Blood Pressure

A new review shows that diuretics — drugs often recommended as a first-line treatment for high blood pressure — are also effective when added as a second agent to other blood-pressure lowering drugs.

Moreover, diuretics are effective regardless of which blood pressure medication the patient takes them with with, found reviewers led by Jenny Chen at the University of British Columbia, in Vancouver. Many people with high blood pressure must take two or more medications to keep their blood pressure in check.

The reviewers analyzed the findings of 53 studies evaluating diuretics in 15,129 patients to see how much blood pressure decreases when patients take a diuretic, like Diuril, with another antihypertensive drug.

The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

Medical professionals define hypertension as a blood pressure measurement of equal to or greater than 140/90 mmHg. Hypertension is a main contributor to heart disease, kidney disease and stroke.

Thiazide diuretics, first developed in the 1950s, can be effective in controlling hypertension and are among the least expensive drugs available for that purpose. Other medications for hypertension — angiotensin-converting enzyme (ACE) inhibitors like Lotensin, angiotensin receptor blockers (ARBs) like Avapro and calcium channel blockers — have been developed since then.

At the beginning of the studies, patients had an average blood pressure of 156/101 mmHg. Their average age was 54 years and most of the patients were white. Studies lasted from three weeks to 12 weeks, six weeks on average.

Hydrochlorothiazide was the diuretic used in nearly all (92 percent) of the studies. Diuretics were added as a second medication to newer blood pressure lowering drugs such as ACE inhibitors, ARBs and calcium channel blockers.

When added as a second drug, thiazide diuretics lowered blood pressure between 4/2 mmHg at lower doses and 14/6 mmHg at higher doses. These results did not depend on the class of first-line drug prescribed.

“The most important finding is that diuretics administered as a second-line drug lower blood pressure to the same degree as when given alone,” Chen said. “Blood pressure reduction appears to be independent of the first-line drug used.”

“The second most important finding,” she added, “is that the blood pressure lowering effect was greater with greater doses. This has not been demonstrated previously in clinical studies.”

Sandra Taler, M.D., a clinician in the division of nephrology and hypertension at the Mayo Clinic, commented on the review. “For certain drugs — ACE inhibitors and ARBs — it’s generally been promoted that adding a diuretic will have a ‘synergistic effect,’” that is, an effect over and above an additive effect. “Adding a diuretic to these drugs should result in a greater reduction in blood pressure than just the single effect of each drug. This study did not find that, and it really didn’t matter what drug the diuretic was added to,” she said.