Angiotensin Converting Enzyme (ACE) Inhibitors

Pharmacy Author: Omudhome Ogbru, Pharm.D.
Medical Editor: Jay W. Marks, M.D.

What are ACE inhibitors, and how do they work?

Angiotensin II is a very potent chemical that causes the muscles surrounding blood vessels to contract and thereby narrows the blood vessels. The narrowing of the vessels increases the pressure within the vessels and can cause high blood pressure (hypertension). Angiotensin II is formed from angiotensin I in the blood by the enzyme, angiotensin converting enzyme (ACE). ACE inhibitors are medications that slow (inhibit) the activity of the enzyme, which decreases the production of angiotensin II. As a result, the blood vessels enlarge or dilate, and the blood pressure is reduced. This lower blood pressure makes it easier for the heart to pump blood and can improve the function of a failing heart. In addition, the progression of kidney disease due to high blood pressure or diabetes is slowed.

For what conditions are ACE inhibitors used?

ACE inhibitors are used for controlling blood pressure, treating heart failure and preventing kidney damage in people with hypertension or diabetes. They also benefit patients who have had heart attacks. In studies, individuals with hypertension, heart failure, or prior heart attacks who were treated with an ACE inhibitor lived longer than patients who did not take an ACE inhibitor. Because they prevent early death resulting from hypertension, heart failure or heart attacks, ACE inhibitors are one of the most important group of drugs. Some individuals with hypertension do not respond sufficiently to ACE inhibitors alone. In these cases, other drugs are used in combination with ACE inhibitors.

Are there any differences among the different types of ACE inhibitors?

ACE inhibitors are very similar. However, they differ in how they are eliminated from the body and their doses. Some ACE inhibitors need to be converted into an active form in the body before they work. In addition, some ACE inhibitors may work more on ACE that is found in tissues than on ACE that is present in the blood. The importance of this difference or whether one ACE inhibitor is better than another, has not been determined.

What are the side effects of ACE inhibitors?

ACE inhibitors are relatively well-tolerated by most individuals. Nevertheless, they are not free of side effects, and some patients should not use ACE inhibitors. ACE inhibitors usually are not prescribed for pregnant patients because they may cause birth defects. Individuals with severe kidney problems and people who have had a severe reaction to ACE inhibitors probably should avoid them. The most common side effects are cough, elevated blood potassium levels, low blood pressure, dizziness, headache, drowsiness, weakness, abnormal taste (metallic or salty taste), and rash. It may take up to a month for coughing to subside, and if one ACE inhibitor causes cough it is likely that the others will too. The most serious, but rare, side effects of ACE inhibitors are kidney failure, allergic reactions, a decrease in white blood cells, and swelling of tissues (angioedema).

With which drugs do ACE inhibitors interact?

ACE inhibitors have few interactions with other drugs. Since ACE inhibitors may increase blood levels of potassium, the use of potassium supplements, salt substitutes (which often contain potassium), or other drugs that increase the body's potassium may result in excessive blood potassium levels. ACE inhibitors also may increase the blood concentration of lithium (Eskalith) and lead to an increase in side effects from lithium. There have been reports that aspirin and other non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen, indomethacin, and naproxen may reduce the effects of ACE inhibitors; however, there is no conclusive evidence that this interaction, if it exists, is important.

What ACE inhibitors are available?

The following is a list of the ACE inhibitors that are available in the United States:

captopril (Capoten), benazepril (Lotensin), enalapril (Vasotec), lisinopril (Prinivil, Zestril) fosinopril (Monopril), ramipril (Altace), perindopril (Aceon), quinapril (Accupril), moexipril (Univasc), and trandolapril (Mavik).

Last Editorial Review: 3/10/2003

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