INDIANAPOLIS -- Two inexpensive but widely overlooked drugs may helpmany patients who continue to have high blood pressure despite takingstandard blood pressure medications, according to research by IndianaUniversity School of Medicine scientists.
Howard Pratt, M.D., and his colleagues studied two compounds --amiloride and spironolactone -- in a group of African-American patientswith high blood pressure. African-Americans are disproportionatelyaffected by high blood pressure, and tend to retain more sodium intheir bodies, which is linked to high blood pressure. Amiloride andspironolactone are diuretics, or "water pills," that have beenavailable for many years but no longer get much attention fromprescribing physicians.
In the study of 98 patients, some were given one of the twodrugs, some were given both, some were given a placebo. All of thepatients continued to take their standard blood pressure medication. Onaverage, blood pressures of the patients taking either amiloride orspironolactone individually, or both drugs, dropped significantly.There were no side effects. The study was published in the Septemberissue of the journal Hypertension.
Uncontrolled blood pressure can lead to serious complicationsincluding heart attack, stroke, and kidney failure. According to someestimates, nearly one in three U.S. adults has high blood pressure.
The two drugs tested work by limiting the amount of sodium thekidneys reabsorb or take back into the body during the process ofproducing urine.
"The kidneys do an incredible job of holding on to sodium,which was important to the survival of our early ancestors who lived ina salt-poor world, but today there's so much salt in the food we eatthat the kidneys end up holding onto too much sodium," said Dr. Pratt.The result, he said, can be high blood pressure -- also known ashypertension.
The kidney retains sodium in two general regions. Traditionaldiuretics reduce the uptake of sodium at an early region, closer towhere blood is filtered to produce urine. A region more "downstream"also takes back sodium from the urine. If too much is taken back in thefirst region, then the kidney adjusts by taking up less sodium in thesecond region. But such an adjustment doesn't always occur, with theresult that the kidney ends up bringing too much sodium back into thebody. This problem may worsen with age, Dr. Pratt said.
Amiloride and spironolactone work on the late or downstreamregion. By inhibiting the uptake of sodium there, "which is the lastplace in the chain of events for getting it right, you can restoreblood pressure to normal levels in many patients when the drugs areused together with a standard diuretic," Dr. Pratt said.
Dr. Pratt said that physicians with patients showing resistanceto treatment -- patients for whom standard therapy doesn't result in anormal blood pressure -- tend to prescribe higher doses of the medicinealready being used, or add in a new blood pressure drug that could beexpensive and often is also ineffective. He said he expects that thisand additional studies will convince physicians to try the amiloride orspironolactone alternatives instead.
Dr. Pratt said the study was conducted with African-Americanpatients because they are on average more predisposed to retain sodium,but he believes the effectiveness of the two drugs likely would be thesame regardless of ethnicity.
The study was funded by a grant from the National Institutes of Health.
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