Like beta-blockers, angiotensin-converting enzyme (ACE) inhibitors keep your body from doing something it would normally do in this case, releasing an enzyme called angiotensin II, which causes your blood pressure to rise. High blood pressure makes your heart work harder. If your heart is already weak, working harder will weaken it further, which can worsen your heart disease and even lead to heart failure.

From Venom to Virtue In the banana plantations of southwestern Brazil, field workers who were bitten by a pit viper snake called Bothros jararaca typically collapsed, due to a sudden and catastrophic drop in their blood pressure. In the late 1960s, scientists discovered why: the snake venom contained a potent substance that inhibited the normal functioning of something called angiotensin-converting enzymes.

Scientists reasoned that if inhibiting these enzymes could drop normal blood pressure to below normal levels, it might also drop high blood pressure to normal levels. That’s exactly what the drugs they developed called “ACE inhibitors” do, though more safely than the snake venom. These drugs have proven to be exceptionally effective, and not just for reducing blood pressure.

In the 1990s, large trials of ACE inhibitors showed that they could not only treat high blood pressure but also improve the survival of people with heart failure and of certain patients who had suffered a heart attack. A more recent study suggested that all patients who have had a heart attack may benefit from ACE inhibitors.

Among patients with heart disease, many of whom were already also taking aspirin and beta-blockers, ACE inhibitors reduced the risk of heart attack by 20 percent, stroke by 30 percent, and death from heart attack or stroke by 25 percent. Moreover, researchers are beginning to discover that ACE inhibitors can protect people with diabetes from developing kidney disease.

If you have heart disease, you should take an ACE inhibitor every day for the rest of your life. If you have heart disease or narrowed arteries but have never had a heart attack or heart failure, it may still be a good idea for you to take an ACE inhibitor.

The most common side effect of ACE inhibitors is a dry cough, which affects 5 to 10 percent of people taking the medication. If the cough is too bothersome, your doctor may recommend an alternative medication, called an angiotensin receptor blocker (ARB, described below).

In addition, some people experience dizziness when they first start taking ACE inhibitors, but this symptom usually decreases with time. Other less common side effects of ACE inhibitors include fatigue, headache, stomach upset, and rashes. If you experience any of these side effects, discuss them with your doctor.

If, in addition to heart disease, you also suffer from severe kidney disease or kidney failure, you’ll need to consult with your doctors about using ACE inhibitors since they can occasionally worsen the function of the kidneys. More often, however, ACE inhibitors are used to prevent kidney failure, particularly in people with diabetes.

If you have an elevated potassium level, ACE inhibitors can also create an increased risk. And of course, should you prove to be allergic to them, you should not continue taking ACE inhibitors. Overall, however, the risks and side effects of ACE inhibitors are far offset by their dramatic benefits.

Frequently Asked Questions

What is the difference between ACE Inhibitors and Angiotensin II Receptor Blockers (ARBS)?

Like ACE inhibitors, ARBs lower high blood pressure and help patients with heart failure. This is why patients who develop side effects from ACE inhibitors, such as a dry cough, are often switched to an ARB. Clinical studies have just recently shown that ARBs, like ACE inhibitors, can also have a powerful effect on lowering a per-son’s risk for heart attack and stroke if he or she has abnormal heart function.

ARBs are considered a “second-line” strategy because more evidence is available to support the use of ACE inhibitors. You should know that the guidelines support the use of ARBs, though less strongly than ACE inhibitors, as ARBs are a relatively newer medication that have been studied less extensively than ACE inhibitors.