Lown Cardiovascular Research Foundation

Harvard Heart Letter | June 2008

A second look at beta blockers and blood pressure

A beta blocker alone isn’t usually the best choice for simple, uncomplicated high blood pressure.

Beta blockers have long been a mainstay for controlling blood pressure when it creeps too high. The first one, propranolol, appeared in 1964. Because it made such a big difference in treating angina (chest pain triggered by exercise or stress) and it shed some light on what regulates the heart, its inventor, Sir James Black, was awarded a Nobel Prize.

Now there are a baker’s dozen of beta blockers approved for treating high blood pressure. You can tell a beta blocker by its generic name — they all end in “lol.” The newest, nebivolol (Bystolic), hit the U.S. market in February 2008.

Millions of Americans take a beta blocker. They are life-prolonging drugs for heart attack survivors, as well as for folks with angina or heart failure. But they are turning out to be a poor choice for simple high blood pressure without other cardiovascular problems.

How beta blockers work

Beta blockers do what their name implies. They block the beta adrenergic receptor, a folded protein that sits on the surface of many cells. Its job is to respond to adrenaline, one of the body’s key stress hormones. Adrenaline, acting through beta adrenergic receptors, makes the heart beat faster and harder. This increases blood pressure.

By acting as a kind of anti-adrenaline, beta blockers slow the heart’s rate and ease the force of its contractions. Blood pressure falls as the heart pumps smaller amounts of blood through the arteries with each beat. Some of the newer beta blockers also make blood vessels relax and offer less resistance to blood flow, further lowering blood pressure.

Over the years, hundreds of studies have shown that the various beta blockers are far better than placebos at lowering blood pressure. An analysis of this body of work by a team at Oregon Health and Science University found that one beta blocker is as good as another in controlling blood pressure. Compared with other types of blood pressure medicines, though, a beta blocker alone for uncomplicated high blood pressure doesn’t always stack up.

Beyond blood pressure

Hypertension isn’t a disease, but an outward sign of trouble in the circulatory system. High blood pressure is worrisome because of the havoc it can wreak throughout the body. High blood pressure can lead to stroke, heart failure, kidney disease, eye damage, and other problems. Keeping blood pressure in check is good, but what you really want from a blood pressure medicine is to keep the complications of high blood pressure at bay. Studies have challenged whether beta blockers should be used as the first line of defense against uncomplicated high blood pressure.

In 2004, the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) was stopped early when it became clear that the combination of an ACE inhibitor and a calcium-channel blocker prevented stroke and other cardiovascular events better than a beta blocker plus a thiazide diuretic (a “water pill”). Major reviews since then have shown that lowering blood pressure with a beta blocker alone doesn’t offer the same protection against stroke, heart attack, or cardiovascular-related death as doing it with a diuretic, ACE inhibitor, or calcium-channel blocker.

The U.S. guidelines on blood pressure published in 2003 put beta blockers on an equal footing with other blood pressure medicines. A statement from the American Heart Association demotes them. It concludes that the evidence is “weak, especially in the elderly” that beta blockers offer the same protection as other blood pressure drugs among people who don’t have coronary artery disease, haven’t had a heart attack, or haven’t developed heart failure. It is likely that similar language will be in the next iteration of the national guidelines.

This new thinking may apply only to the older beta blockers, propranolol, atenolol, and metoprolol. Newer ones like carvedilol and labetalol also block the alpha adrenergic receptor in blood vessel walls. This receptor acts to constrict blood vessels. Blocking it helps blood vessels relax. This decreases resistance to blood flow and lowers blood pressure. The newest beta blocker, nebivolol, stimulates the release of a tiny molecule called nitric oxide that relaxes the smooth muscle that lines artery walls. The newer beta blockers may prevent heart attack, stroke, heart failure, or premature death as well as other blood pressure drugs, but that remains to be seen.

It is also possible that stopping a beta blocker is what makes these drugs lag behind others. Half or more of people who start taking a beta blocker stop within a year, often abruptly, and often without telling their doctors. Side effects are the usual culprit. Common ones include drowsiness or fatigue, cold hands or feet, and a dry mouth, eyes, or skin.

Quitting cold turkey can be dangerous. As the heart begins to beat faster and harder, it requires more oxygen. If narrowed coronary arteries can’t meet these new demands, chest pain can follow. Increased pressure inside blood vessel walls can erode and break open artery-clogging plaque, possibly leading to a heart attack or stroke. Sudden withdrawal can also lead to erratic heart rhythms and sudden death.

When to use a beta blocker

These criticisms of beta blockers are aimed only at their solo use to treat uncomplicated high blood pressure. If you have had a heart attack, you should be taking a beta blocker, even if your blood pressure is normal. If it is high, then a beta blocker is an excellent choice for lowering it. A beta blocker can extend life for people living with angina, heart failure, or an arrhythmia like atrial fibrillation. A beta blocker is also a good add-on when a diuretic, ACE inhibitor, or other medication isn’t enough to get blood pressure into the safety zone.

For fighting uncomplicated high blood pressure, though, a beta blocker alone might not be the best choice. If you are just finding out you have high blood pressure and your doctor recommends that you take a beta blocker, ask about alternatives. (Be forewarned, though — a survey showed that most doctors think that beta blockers are the most effective class of medication for lowering blood pressure.) If you are already taking a beta blocker for uncomplicated high blood pressure, ask your doctor why. If he or she doesn’t have a good reason, slowly switching over to a thiazide diuretic, ACE inhibitor, or other type of medication might be a good idea.

Whatever you do, don’t stop taking a beta blocker without first talking with your doctor. Most experts agree there’s no urgent need to switch if it is working for you, and suddenly stopping the drug can have disastrous consequences.

Help your medications

Drugs aren’t the only way to keep your blood pressure in check. In fact, for most people they should be started only if lifestyle strategies aren’t enough to do the job on their own. No pill can take the place of a healthful diet and physical activity. Here are some drug-free strategies for lowering blood pressure.

Low-pressure diet. The DASH diet is a proven approach to controlling blood pressure. It involves eating more fruits, vegetables, whole grains, fat-free or low-fat dairy products, fish, poultry, beans, and nuts while cutting back on salt, added sugars, saturated fat, and red meat. Following the DASH diet can lower systolic blood pressure by 10 to 22 mm Hg. That’s better than most medications can do. (To learn more about this diet, visit health.harvard.edu/122.)

Physical activity. Walking for 30 minutes a day can lower systolic blood pressure by 9 mm Hg or more.

Weight control. If you are overweight, shedding 5% to 10% of your weight can yield a drop in blood pressure of 5 to 20 mm Hg.

Alcohol in moderation. Moderate alcohol intake — meaning one to two drinks a day for men, no more than one drink a day for women — has little effect on blood pressure. Heavy drinking, however, can substantially boost it.

Stress control. Reducing stress, or fighting its effects with exercise, yoga, meditation, or other techniques can help you keep your pressure down.