Lown Cardiovascular Research Foundation

Harvard Heart Letter | February 2008

Angiotensin inhibitor or blocker?

For controlling blood pressure, an ACE inhibitor is a good place to start.

Doctors are often quick to prescribe new drugs even when the “old” ones work perfectly fine. That has certainly been the case with newer angiotensin receptor blockers (ARBs) and older ACE inhibitors, two classes of drugs commonly used to treat high blood pressure (hypertension). Both drugs target a molecule known as angiotensin II, but in different ways.

ACE inhibitors block the conversion of inactive angiotensin I into active angiotensin II. Less angiotensin II in circulation gives blood vessels a chance to relax and widen, easing the passage of blood. ACE inhibitors also protect the kidneys in people with diabetes and kidney trouble, and they slow the dangerous cardiac remodeling that often occurs with heart failure. The first ACE inhibitor was approved in 1981.

ARBs don’t interfere with the production of angiotensin II. Instead, they prevent it from latching onto and activating receptors on the surface of blood vessel cells. This also helps arteries relax. The first ARB was approved in 1995.

Comparing apples and apples

How do the newer ARBs compare with the older ACE inhibitors? Pretty well, according to a comprehensive review of 61 head-to-head trials comparing the two types of drugs for hypertension. For lowering blood pressure, ARBs work as well as ACE inhibitors, but they aren’t superior to the older drugs. Neither type of drug affects cholesterol or blood sugar levels, and they rarely cause serious problems. Both can generate a dry cough, though this is more common with ACE inhibitors (affecting up to 10% of people) than ARBs (affecting up to 3% of people). According to the review, which was published in the January 1, 2008, Annals of Internal Medicine, about 8% of people stop taking an ACE inhibitor because of side effects, compared with about 4% of people taking an ARB.

Long-term effects

Since hypertension isn’t “curable,” most people who have it take blood pressure–lowering medications for years. The jury is still out on how effective each drug is for preventing heart attack, stroke, early death, and other major cardiovascular events. Bigger studies are needed to see if ACE inhibitors and ARBs are truly comparable, and how each one stacks up against taking both drugs, which some people do.

Given how similar these drugs are, it makes sense to start with an ACE inhibitor. Almost all of them are available as generics, some for just 25 cents a day. In contrast, ARBs are available only in brand-name forms and cost $2 to $3 a day. If an ACE inhibitor gives you a cough, then trying an ARB makes sense.