Angiotensin inhibitors are medications used principally to treat high blood pressure, which they accomplish by affecting the renin-angiotensin-aldosterone (RAA) system in the body. There are two common types of these drugs, called angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs). These affect the RAA system differently, but they have similar cumulative effects. ACE inhibitors may be slightly more effective, but ARBs are sometimes preferred because they may not cause certain adverse reactions as often. It’s worth noting that both medications tend to have comparable side effects in most instances.
The RAA has a role in regulating blood pressure because it produces angiotensin II, which binds to receptors in its system that signal blood vessels to contract. This narrowing results in higher blood pressure, as the body must work harder to move the blood from place to place. All angiotensin inhibitors affect the RAA in certain ways that reduce contraction of the veins and arteries, so that blood moves more easily. Blood pressure is lowered as a result.
ACE inhibitor medications, like captopril, enalapril, and lisinopril, belong to one of the two classes of angiotensin inhibitors. These drugs deplete a substance called angiotensin-converting enzyme. When ACE is reduced, angiotensin I cannot readily convert to angiotensin II. This means there are fewer signals sent to the blood vessels to narrow, resulting in less resistant blood flow.
ARBs are the other main form of angiotensin inhibitors. Some examples of these medications are losartan, candesartan, and telmisartan. These don’t affect the amount of angiotensin II produced. Instead, they bind to receptors in the RAA system that angiotensin II would ordinarily use. This prevents the chemical from signaling the blood vessels to contract.
Angiotensin inhibitors provide powerful methods to lower blood pressure through action on the RAA system. One difference noted between the two types of medication include that ACE inhibitors also signal the body to produce nitrous oxide, which may more strongly affect dilation of the blood vessels. On the other hand, ACE inhibitors can be associated with the development of a persistent cough in some patients, whereas ARBs tend to cause this side effect less frequently. Some physicians view ARBs as appropriate back-up medications if patients react poorly to ACE inhibitors.
In other respects, angiotensin inhibitors of both types are very similar. ARBs or ACE inhibitors may be prescribed for not only high blood pressure, but for conditions like congestive heart failure or treatment after a heart attack. Drugs of either kind also have comparable side effects, such as dizzy sensations, stomach upset, and headaches. Aside from persistent cough, which occurs more commonly with ACE inhibitors, adverse reaction incidence tends to be low.