Popular prescription medications taken to control hypertension may actually boost blood pressure in a "statistically significant" percentage of patients, researchers report.
The warning stems from a new study appearing in the online edition of the American Journal of Hypertension. The research involved 945 New York City residents participating in a program designed to control high blood pressure in the workplace from 1981 to 1998.
"Every clinician knows that there's a variation in response to antihypertensive treatment, and that some patients will have an elevation in blood pressure," study author Dr Michael Alderman, a professor of epidemiology & population health and of medicine at the Albert Einstein College of Medicine of Yeshiva University and a former president of the American Society of Hypertension, said in a news release from the society. "
Patients fail to take their medications
The latter phenomenon is generally attributed to patients' failure to take their medications or to a random event. But these data show that it's not a random event."
None of the study participants, who all had systolic blood pressure of at least 140 mm Hg, had been treated for high blood pressure prior to enrollment in the study.
Once enrolled, they were prescribed just one of two types of blood pressure medications: either a so-called "V" drug to lower blood volume (by means of a diuretic or a calcium channel blocker), or a so-called "R" drug (a beta blocker or ace inhibitor) to lower the kidney enzyme renin that is critical to blood pressure control.
After monitoring and reviewing both plasma renin activity (PRA) and systolic blood pressure levels during treatment, Alderman and his team found that the plasma renin levels predicted whether a "V" or an "R" drug would benefit or be problematic for a particular patient.
Significant blood pressure increase
Overall, 7.7 of the patients had a clinically significant increase in blood pressure of 10 mmHg or more. The highest percentage of these responses 16% occurred in patients with low renin levels who were given an "R" drug (a beta blocker or an ACE inhibitor).
Rather than a random event, an elevation in blood pressure from a particular drug suggested "a mismatch between the patients' renin status and the drug," Alderman said. "Our findings suggest that physicians should use renin levels to predict the most appropriate first drug for treating patients with hypertension."
For example, the researchers wrote, "our data indicate that patients with low PRA values are at highest risk" of a clinically significant increase in systolic blood pressure when prescribed an R drug.
Tracking renin levels would be particularly helpful for two groups of patients, Alderman and his colleagues noted: those taking blood pressure medications for the first time, and those already on a regimen incorporating several blood pressure drugs at the same time.
Renin level monitoring "would increase the likelihood of achieving blood pressure control and reduce the need for patients to take additional antihypertensive medication," Alderman added.
Test is expensive and hard to do
Plasma renin activity testing has been used for years to determine the underlying cause of an individual's hypertension (whether it is caused by too much blood volume or constricted blood vessels, or both), but the test was expensive and hard to perform accurately.
On an encouraging note, the research team points out that in recent years testing for plasma renin activity has become more effective and more widely available than it was in the past.
Dr Stephen A. Siegel, an assistant clinical professor of medicine at New York University, agreed that renin monitoring could be an "excellent approach" if clinicians are able to identify an enzyme level dividing line that clearly separates those patients who would benefit from a particular medication from those that might not.
Addressing the problem
"We've been looking at renin levels for a long time," he said, "but it's been of equivocal benefit in the past because it's been hard to agree on a particular stable level that would indicate trouble. So I'm a little hesitant to enthusiastically endorse this method for addressing the problem."
"However, we're getting more sophisticated with this, and improvements in the testing may now make it much more helpful for screening purposes," Siegel added. "And certainly, conceptually, the problem this paper addresses is real because not everyone is the same.
Whereas in the 60s and 70s, our choices in anti-hypertensives were extremely limited and blunt, today there is a lot of work being done to individualize patients to see what treatment works best case by case, instead of lumping them all together in the single category of having high blood pressure.
So, this type of work is very important."
(Health Day/ August 2010)
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