TUESDAY, March 22 (HealthDay News) -- Many older people struggling with high blood pressure are being inappropriately and unnecessarily prescribed a combination blood pressure medications, a team of Canadian researchers warns.

And, they caution, the often unwarranted dual protocol can have serious consequences: an increased risk for kidney failure and even death.

The two types of drugs in question are angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs).

On their own, each is well established and highly effective for controlling blood pressure, the study team stressed. Also, a small number of people -- those diagnosed with a particular blood pressure issue related to improper left ventricular systolic function -- may derive some added benefit from taking the two medications concurrently, they say.

But most seniors do not need both drugs, the researchers contend, particularly given the fresh indication that there is usually far more to lose than gain.

"I'm not surprised that use of this combination of agents was often not guideline-based, as often the assumption is made that, if two drugs alone are beneficial, then the combination of the two must be even more beneficial," said the study's lead author, Dr. Finlay A. McAlister, from the division of general internal medicine and the Mazankowski Alberta Heart Institute at the University of Alberta in Edmonton, Canada.

But McAlister noted that research has already indicated that this is not the case with the mixing of ACE inhibitors and ARBs, and the new study "confirms the risks of this combination." The findings were reported March 21 in the Canadian Medical Association Journal.

The research involved 32,312 people, all older than 65, who were taking either an ACE inhibitor alone, an ARB alone or a combination of the two.

The team noted that among the roughly 5 percent who took both medications, the vast majority -- more than 86 percent -- did not have a condition that justified a combination regimen.

They also found that those on a combination therapy did not closely adhere to the regimen; most had stopped taking the drugs within three months, even in the absence of serious illness or side effects. The researchers speculated that the onset of low blood pressure was the prime reason for abandoning the routine.

Those who stuck to the dual-drug protocol were found to be more likely to experience end-stage renal disease or kidney failure or to die than were those taking either of the drugs alone.

Dr. Bryan Henry, an assistant professor of medicine with Finger Lakes Cardiology Associates at the University of Rochester Medical Center in New York, expressed little surprise with the findings.

"There's been mounting evidence for years that the combination either doesn't add anything or that it can be harmful," Henry said. "For some small subset of patients, it might help. But all in all, these drugs shouldn't be used in combination."

"But readers," Henry hastened to add, "should not take home the message from this that each drug individually is not safe and effective. It's just the combination that's a problem."

Dr. Gregg C. Fonarow, a cardiology professor at the University of California, Los Angeles, expressed hope that the medical community would take heed of the apparent risks involved with combining the two meds.

"A number of trials have failed to show any added benefit from taking both drugs together, and the combination is not usually recommended in treatment guidelines," he noted. "So it's actually surprising that so many patients were receiving it anyway."

"But now this is an opportunity for physicians to become aware of the risks outweighing the benefits for patients," Fonarow added. "It's certainly a risk that should be avoided."

More information

The American Heart Association has more on blood pressure medications.