Your body is equipped with an extraordinary variety of internal communication systems—chemical and electrical pathways through which signals are communicated. The primitive “fight or flight” response we all feel when suddenly confronted with something stressful is regulated by a system of beta-adrenergic receptors that exist in tissues throughout your body.

They respond to the release of a hormone produced in your adrenal gland by, among other things, speeding up your heart and increasing its demand for oxygen and preparing you to confront the challenge. That’s exactly what you want to have happen when faced with an emergency—unless, that is, you have heart disease.

In that case, the very same response system your body has designed to save you can, instead, hurt you. So-called beta-blockers—invented by Scottish researcher Sir James Black in the 1960s—keep those receptors from responding, keep your heart from racing and beating hard, and thus reduce your heart’s need for oxygen.

Black created them to reduce the pain of angina, but a 1981 study found that beta-blockers helped prevent second heart attacks. The researchers were so excited by this finding that they ended the study early so that patients in the control group (the ones taking the placebo) could also take beta-blockers.

Other studies have since confirmed this result, demonstrating that beta-blockers can reduce the odds of having another heart attack or of dying by at least 25 percent. And that’s not all.

Beta-blockers have also been found to be effective at preventing and treating irregular heartbeats, heart failure, and high blood pressure, reducing stress on the heart, and decreasing the amount of injury that occurs during a heart attack. Indeed, beta-blockers may even decrease scarring of the heart muscle following a heart attack.

Since Sir James Black’s discovery, for which he received the Nobel Prize, beta-blockers have become the cornerstone medication for people with heart problems, from angina to heart attacks to heart failure. If you’ve had any of these conditions, the chances are your doctor will prescribe a beta-blocker for you to take indefinitely.

Many kinds of beta-blockers have been created over the years, including acebutolol, atenolol, betaxolol, bisoprolol, carteolol, carvedilol, labetalol, metoprolol, nadolol, penbutolol, pindolol, propanolol, sotalol, and timolol. Precisely which type and dose of beta-blocker you take will depend upon the heart condition for which your doctor prescribes it and how well you tolerate its side effects.

In addition, beta-blockers differ in how long they last in the body. Longer-lasting beta-blockers can be taken less frequently. You’ll want to discuss all of these factors with your doctor when considering which beta-blocker to choose.

Most people taking beta-blockers experience few side effects. When they do, these effects typically are minor and disappear with time. Fatigue is the most common side effect—and, consequently, athletic patients may feel that they are unable to perform at peak levels. Sexual dysfunction has also been associated with beta-blockers.

But both of these side effects are not very common. In an analysis of a large number of clinical trials, involving more than 30,000 individuals, the researchers found that beta-blockers were associated with increased fatigue in only 18 of every 1,000 people treated and with sexual dysfunction in only 5 of every 1,000 people.

Since these same symptoms can occur in any patient with heart disease, they can often be wrongly attributed to beta-blockers. In addition to these effects, patients with peripheral vascular disease (narrowing of the arteries to the legs) may find that the pain they feel when walking increases.

A few patients may find that their heartbeat slows so profoundly that they feel weak or dizzy. In general, however, the risk of these side effects is far offset by the benefit of the medications. Also, some people believe that beta-blockers increase the risk of depression, but the studies have not supported that concern.

If you already have a very slow heart rate or if you have a propensity for a slow heart rate and do not have a pacemaker, you shouldn’t be taking beta-blockers (this is something to discuss with your doctor). In addition, if you suffer from asthma, you should know that beta-blockers can trigger or worsen asthma symptoms.

If your asthma is mild to moderate, though, studies show that some types of beta-blockers may be safe for you. For the vast majority of people with heart disease, however, the benefits of beta-blockers far outweigh the risks. If you’re concerned about possible side effects or risks, you and your doctor may consider a trial period. If you do not tolerate beta-blockers, they can be discontinued.

Frequently Asked Questions

Can I take a Beta-Blocker if I have chronic obstructive pulmonary disease (COPD) or emphysema?

COPD, also known as emphysema or chronic lung disease, is a condition that commonly, but not always, occurs as a result of long-term smoking. It limits your ability to breathe, and patients with this condition often need many medications. Some people with this problem cannot take beta-blockers.

Others, with milder forms of lung disease, can give beta-blockers a try. While beta-blockers can affect many organs in the body, including the lungs, certain beta-blockers are “cardioselective,” which means that their actions target the heart more specifically. These beta-blockers, such as metoprolol and atenolol, are safer for patients who have COPD.

Are there Beta-Blockers in eyedrops?

Certain types of eyedrops, designed to treat glaucoma, contain beta-blockers. Even though the medication goes in the eyes, it can be absorbed into the body and affect the heart.

Sometimes the doctor who is prescribing the eyedrops is different from the doctor prescribing your heart medications, so be sure that all your doctors know about all the medications you are taking. Some people do take beta-blockers by eyedrops and pills at the same time—but only under close supervision and with careful attention to the dosage.

Should I take Beta-Blockers if I have heart failure?

Heart failure is a condition in which the pumping or filling function of the heart is impaired. Since beta-blockers relax the heart, doctors have long been concerned that these drugs might further weaken a damaged heart.

Now, however, there is strong evidence that the effect is just the opposite and beta-blockers have become a preferred therapy for patients with heart failure. In a patient with heart failure, a beta-blocker must be started at a low dose and then increased slowly, but it produces a remarkable benefit.

Do Beta-Blockers cause depression?

Some researchers have suggested that beta-blockers may cause depression. Although they do affect the brain as well as the heart, a comprehensive survey of all the studies of beta-blockers failed to show that people taking beta-blockers suffer from depression any more than people who do not take them. Therefore, expert opinion is that beta-blockers do not put you at a substantially higher risk of being depressed.