Commonly prescribed drugs used to lower blood pressure can actually have the opposite effect-raising blood pressure in a statistically significant percentage of patients, a new study has said.
The study by researchers at Albert Einstein College of Medicine of Yeshiva University suggests that doctors could avoid this problem-and select drugs most suitable for their patients-by measuring blood levels of the enzyme renin through a blood test that is becoming more widely available.
"Our findings suggest that physicians should use renin levels to predict the most appropriate first drug for treating patients with hypertension," says lead author Michael Alderman, professor of epidemiology and population health and of medicine at Einstein.
The study involved 945 patients who were enrolled in a workplace antihypertensive treatment program in New York City from 1981 to 1998. All had a systolic blood pressure (SBP) of at least 140 mmHg. SBP, the top number in the blood pressure reading, represents the amount of force that blood exerts on the walls of blood vessels when the heart contracts. No patients were receiving treatment for high blood pressure before enrolling in the study.
The patients were given a single antihypertensive medication, either a diuretic or a calcium channel blocker (so-called "V" drugs, which lower blood volume) or a beta blocker or an ACE inhibitor ("R" drugs, which lower levels of renin, an enzyme secreted by the kidneys that plays a key role in maintaining blood pressure).
Plasma renin activity (PRA) and SBP were measured at enrollment, and SBP was measured again after one to three months of treatment. The renin level predicted those patients who were most likely to have a favorable response with either an R or a V drug. In addition, for both R and V drugs, the renin test was able to identify those patients most likely to experience a "pressor response"- a clinically significant increase in SBP of 10 mmHg or more.
Overall, 7.7 percent of the patients exhibited a pressor response. The highest percentage of pressor responses-16 percent-occurred in patients with low renin levels who were given a beta blocker or an ACE inhibitor (R drugs).
Alderman says that two groups of patients might especially benefit from having their renin levels measured: patients being prescribed antihypertensive drugs for the first time and patients who are taking multiple antihypertensive drugs when one or two might work just as well. "With renin testing, you will more often get blood pressure under control with less therapy," he adds.
The study appears in the online edition of the American Journal of Hypertension.