Jan 11, 2011 10:30 PM
Jan. 11, 2011 -- Blood pressure drugs in the class known as angiotensin II receptor blockers (ARBs) reduce mortality in patients with heart failure, but new research suggests that not all work equally well.
The analysis included more than 30,000 patients enrolled in a Swedish heart failure registry.
At one year, 90% of patients taking candesartan were still alive, compared to 83% of patients taking losartan. After five years, 61% of candesartan patients and 44% of losartan patients were living.
The study appears Jan. 12 in the Journal of the American Medical Association.
The naturally occurring hormone angiotensin II causes blood vessel walls to constrict and narrow, leading to an increase in blood pressure. ARBs lower blood pressure by blocking the action of angiotensin II.
Although the drugs have never been compared head to head for the treatment of heart failure, there have been suggestions that some ARBs are more effective than others.
In a 2007 study involving patients who were 65 and older, survival rates among patients taking losartan were worse than rates for patients taking other ARBs, including candesartan, irbesartan (Avepro), and valsartan (Diovan).
The findings suggested that the benefits derived by heart failure patients were not due to an ARB class effect.
The newly published study raises more questions about a class effect, but they do not mean that patients taking losartan need to stop taking the drug or switch to another ARB, American Heart Association spokesman Clyde W. Yancy, MD, tells WebMD.
Yancy is chief of cardiology at Chicago's Northwestern University Feinberg School of Medicine.
"The bottom line is this should not change clinical practice," he says. "We have seen nothing that raises concerns that this drug or any other angiotensin receptor blocker causes harm."
In several previous studies examining ARBs in the treatment of heart failure, benefits were limited to patients with compromised heart function, as evidence by reduced left ventricular ejection fraction (LVEF).
The Swedish study included patients with and without reduced LVEF, and the survival benefit among patients taking candesartan was seen in both groups.
Although he says more research is needed to confirm the findings, researcher Lars H. Lund, MD, PhD, of Sweden's Karolinska University Hospital says it is not too soon to consider switching some patients on losartan to another ARB.
"If all other things are equal, patients probably should be switched," he says.
Lund tells WebMD that he and other study investigators have received research grants from ARB manufacturers, but no pharmaceutical industry money was used to fund the latest study.
A spokeswoman for losartan manufacturer Merck tells WebMD that although the study suggests a difference between the drugs, it does not prove this.
"Observational analyses (like this study) have limitations and as such do not offer the rigorous study design and results that are provided by well-designed, prospective, controlled clinical trials," Lee Davies of Merck says in a statement. "That is why clinical trials are regarded as the 'gold standard' of scientific evidence."
Yancy says most heart failure patients in the United States who are on losartan are probably taking the drug for high blood pressure.
"I see no benefit in switching these patients from losartan to another drug," he says.