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Around Harvard
This article originally appeared in the August 2007 Harvard Health Letter and is provided courtesy of Harvard Health Publications.
Betting on beta blockers
They’re versatile and have a long track record. But should you count on a beta blocker to treat your high blood pressure?
Beta blockers — also known as beta-adrenergic blockers or beta antagonists — are among the oldest heart medicines. Propranolol (Inderal), the first drug in the class, was developed in the late 1950s. Many others have come along since, including atenolol (Tenormin), bisoprolol (Zebeta), and metoprolol (Lopressor, Toprol XL). If you’re not sure whether a drug is a beta blocker, check its generic name. All the beta blockers end in -lol.
The heart is regulated by the autonomic (think “automatic”) part of the nervous system, which controls involuntary muscle action. Adrenaline (also called epinephrine) and a similar chemical called norepinephrine play an important role in the autonomic system by acting on specific receptors — namely, beta receptors. When adrenaline attaches to those receptors on heart muscle cells, the heart beats faster and more forcefully — tending to raise blood pressure.
Beta blockers are the anti-adrenaline: They work by keeping adrenaline from acting on beta receptors. The result is a slower heart rate (sometimes in the range of 50 beats a minute compared with 60 or more for most adults) and smaller amounts of blood pumped per beat. Blood pressure falls, and the heart’s workload lessens.
Many uses
Beta blockers have become cardiac jacks-of-all-trades. Although they’re perhaps best known as a treatment for high blood pressure, they’re also used for angina (chest pain from the heart muscle not getting enough oxygen), various arrhythmias (such as atrial fibrillation), and congestive heart failure (a weakening of the heart’s pumping action). If you’ve had a heart attack, taking a beta blocker is considered one of the best ways to ward off a second one. And if you’re having coronary bypass surgery, taking a beta blocker before the operation appears to reduce complications and improve survival.
Surgeons have started using beta blockers in their noncardiac cases. Patients usually start taking them several hours before surgery and then for several days afterward. During the operation the beta blockers are given as a continuous infusion.
Even further afield, beta blockers are used to treat everything from tremors to stage fright.
Some doubts
Some study results have stirred up a few doubts about beta blockers. The Anglo-Scandinavian Cardiac Outcomes Trial was a huge study that compared a combination of an ACE inhibitor and a calcium-channel blocker with a combination of a beta blocker and a thiazide diuretic. In 2004, the investigators stopped the trial early because the ACE inhibitor and calcium-channel blocker were proving to be so much more effective at preventing cardiovascular events, particularly strokes.
In 2006, Dr. Eric Taylor, a Harvard Medical School researcher, and his colleagues reported results that showed people taking beta blockers or thiazide diuretics were more likely to develop diabetes. ACE inhibitors and calcium-channel blockers didn’t carry a diabetes risk.
Finding the best one
Writing in the medical journal BMJ in 2007, Dr. H.T. Ong, a Malaysian cardiologist, described the different benefits and optimal uses of the various beta blockers. Some are particularly effective for treating congestive heart failure; others, for preventing the recurrence of heart attacks; and still others, for reducing the likelihood of coronary artery disease.
People also vary in how they respond to beta blockers. Your age could be a factor. A meta-analysis published in the Canadian Medical Association Journal in 2006 found that beta blockers were much less effective in people over age 60.
Authors of a commentary in the Journal of Clinical Investigation noted that genetically determined differences in the shape of beta receptors may account for variations in responses to beta blockers. Such variations might explain differences among ethnic groups. It’s well documented that beta blockers are less effective for treating heart failure in African Americans than in white or Hispanic patients.
The upshot
Beta blockers are multipurpose drugs that have saved a lot of lives or made them better. If you’re taking a beta blocker for high blood pressure and it’s working, most experts say there isn’t any urgent need to switch. But some doctors don’t recommend beta blockers as the first choice for newly diagnosed high blood pressure, unless you have other conditions that might benefit from taking them.
