Angiotensin II receptor blockers (ARBs) are medications that lower blood pressure and are commonly prescribed for the treatment of high blood pressure (hypertension) and heart failure. These medications produce similar effects to ACE inhibitors but by a different mechanism.
Angiotensin II is a substance in the body that signals blood vessels to constrict or narrow. Both ACE inhibitors and ARBs inhibit the effect of angiotensin II and therefore cause blood vessels to widen, reducing blood pressure and the workload of the heart. However, whereas ACE inhibitors work by lowering levels of angiotensin II, ARBs prevent (or block) angiotensin II substance from entering receptors in the smooth muscles of the heart and blood vessels.
In addition, ACE inhibitors decrease the breakdown of bradykinin, a protein that has a powerful influence on the contraction of smooth muscle, such as the heart. ARBs have no effect on bradykinin.
Despite their similarities, these two types of medications are not interchangeable. Research is still trying to determine exactly which patients are more likely to benefit from ARBs. ARBs are generally more expensive than ACE inhibitors, but do not cause the coughing that is a common side effect of ACE inhibitors. This may be related to their lack of effect on bradykinin.
Research into the potential benefits of ARBs for high blood pressure, heart failure and other cardiac conditions is still ongoing. Trials are under way to examine whether ARBs can also be used in combination with other blood pressure lowering medications – a practice that is becoming more frequent with ACE inhibitors. It appears that ARBs are more effective in some cases when used in conjunction with a diuretic, another drug used for high blood pressure. Currently, ARBs are primarily used in patients who cannot tolerate the side effects produced by ACE inhibitors.
About angiotensin-II receptor blockers (ARBs)
Angiotensin II receptor blockers (ARBs) are medications that lower blood pressure and may be used in the treatment of high blood pressure (hypertension). A relatively new medication, they produce similar effects as angiotensin converting enzyme (ACE inhibitors but by a different mechanism.
Both medications work by affecting a substance in the body called angiotensin II. Angiotensin II signals the blood vessels to constrict or narrow. In some people, angiotensin II may cause several adverse effects in the body, including high blood pressure and an increased risk of certain heart conditions.
ACE inhibitors directly lower levels of angiotensin II in the body by preventing the conversion of inactive angiotension I to active angiotensin II. Conversely, ARBs reduce the effect of angiotensin-II by blocking it from entering angiotensin II receptors in the smooth muscles of the heart and blood vessels.
As a result of either medication, blood vessels dilate or relax, and blood pressure is reduced. Both ACE inhibitors and ARBs belong to a category of medications called vasodilators.
ARBs are not interchangeable with ACE inhibitors. ARBs are more reliable for consistently blocking the effects of angiotensin II. However, this research has not yet translated into additional medical benefits of ARBs when compared to ACE inhibitors. ARBs are generally more expensive than ACE inhibitors, but do not cause the most common side effect of ACE inhibitors – a dry, persistent cough.
In addition, ACE inhibitors decrease the breakdown of bradykinin, a protein that has a powerful influence on the contraction of smooth muscle, such as the heart. Bradykinin has been found to cause low blood pressure (hypotension). It is not known whether the ACE inhibitor’s effects on bradykinin are helpful or harmful to the body. ARBs have no effect on bradykinin.
Currently, ARBs are primarily used in patients who are intolerant to ACE inhibitors. Although, they are not usually used as a first option, ARBs are sometimes used in addition to ACE inhibitors to treat heart failure. They are generally taken in tablet form.
ARBs include medications such as:
candesartan eprosartan irbesartan losartan
olmesartan telmisartan valsartan
Conditions treated with ARBs
Angiotensin-II receptor blockers (ARBs) are prescribed for a variety of conditions, including:
High blood pressure (hypertension). A condition in which blood is pumped with excessive force against the artery walls. ARBs cause blood vessels to relax, or dilate, reducing blood pressure. They may be used alone or in combination with other blood pressure-lowering medications (antihypertensives).
Heart failure. A condition in which one or more of the heart’s chambers is not pumping well enough to meet the body’s demands. By lowering blood pressure, ARBs reduce the workload of the heart. Though some types of ARBs are used in the treatment of heart failure, others might worsen this condition. In some cases, ARBs may be used in addition to angiotensin converting enzyme (ACE) inhibitors to treat heart failure.
Type 2 diabetes. A metabolic condition in which the body's tissues cannot properly absorb blood sugar (glucose) from the blood, because of either a lack of, or inability to utilize, insulin. As a result, glucose levels can rise to dangerously high levels in the bloodstream rather than nourishing the body’s tissues, which can lead to complications such as kidney damage. Certain ARBs (e.g., irbesartan, losartan) may be prescribed in patients with both type 2 diabetes and high blood pressure to reduce the risk of kidney failure. ARBs have also been shown to decrease proteinuria (an abnormal leakage of protein into the urine) in patients with type 2 diabetes.
Left ventricular hypertrophy (LVH). A condition in which the heart’s lower-left chamber (left ventricle) has grown thicker or larger due to an underlying cardiovascular condition, causing strain on the heart. The most common cause is high blood pressure. Certain ARBs (e.g., losartan) may be prescribed in patients with both LVH and high blood pressure.
Conditions of concern with ARBs
Certain conditions increase the risk of side effects or other potential problems for patients taking angiotensin-II receptor blockers (ARBs). These include:
Previous allergic reaction to ARBs or similar medications (e.g., ACE inhibitors).
Valvular stenosis (particularly in the aortic or mitral valves). A condition in which there is a narrowing, stiffening, thickening or blockage of one or more heart valves.
Angioedema. A type of edema (swelling) in the head, neck, face, ankles or legs that can lead to difficulty breathing or swallowing.
Kidney or liver disease. Blood pressure-lowering effects of ARBs may be increased in patients with these conditions.
Pregnancy. ARB use may cause birth defects.
Dehydration. Blood pressure-lowering effects of ARBs may be increased in dehydrated patients.
Potential side effects with ARBs
Though the potential for side effects exists with all medications, angiotenisn-II receptor blockers (ARBs) have few common side effects. In fact, one benefit of ARBs is that they generally do not cause the most common side effect associated with angiotensin converting enzyme (ACE inhibitors – a dry, persistent cough.
One potentially serious side effect is hyperkalemia – an abnormally high level of potassium in the blood. However, patients taking ARBs usually have regular blood tests to check potassium levels and therefore avoid any serious consequences. Other serious side effects may occur with ARBs, but are rare. People should seek medical attention immediately for any side effects of hyperkalemia or an allergic or other severe reaction to ARBs, including:
Fainting (syncope)
Dizziness or lightheadedness
Difficulty swallowing or breathing
Shortness of breath
Edema (swelling), especially in the head, face or neck
Abdominal pain or vomiting
Persistent nausea or diarrhea
Skin rash, with or without itching
Chest pain or palpitations
Unusual cough or congestion
Persistent headache
Flu-like symptoms (with or without fever)
Joint or muscle pain or weakness
Other potential side effects of ARBs include:
Headache
Nausea or upset stomach
Drowsiness, weakness or fatigue
Runny nose or sinus pain
Sore throat or cough
Depression or anxiety
Back pain
Salty or metallic taste in mouth
Drug or other interactions with ARBs
Patients should consult their physician before taking any other medication (either prescription or over-the-counter), herbal remedies or nutritional supplements. Of particular danger to individuals taking A-II receptor blockers (ARBs) are:
Potassium supplements. Use increases the risk of hyperkalemia (too much potassium in the body).
Salt substitutes or other low-salt products that use potassium chloride. Use increases the risk of hyperkalemia.
Diuretics (some types). Medications that stimulate the kidneys to produce more urine, flushing excess fluids and minerals (e.g., sodium) from the body. Most diuretics cause the body to lose potassium, as well as sodium and fluids. One type – potassium-sparing diuretics – actually preserves potassium while flushing other minerals from the body. Because of this, using potassium-sparing diuretics in conjunction with ARBs may increase the risk of hyperkalemia.
It is important to note that potassium-sparing diuretics may be also be prescribed to treat high blood pressure. To avoid potentially dangerous complications, patients should be sure to tell their physician about any medication or remedy they are taking before starting a new medication.
Nonsteroidal anti-inflammatory drugs (NSAIDs). These can decrease the effectiveness of the ARBs, worsen high blood pressure or increase the risk of kidney problems. Patients should consult with their physician before using them. A possible exception to this is aspirin. Though aspirin is technically a type of NSAID, research has suggested that aspirin use – especially the low doses associated with daily aspirin therapy – may be beneficial for heart patients. Patients should discuss the potential benefits and risks of aspirin therapy with their physicians.
Insulin and antidiabetic medications. Use of certain ARBs may increase the effect of these medications on insulin levels in the body.
Some antidepressants (e.g., lithium). Use of certain ARBs can prevent these medications from being removed from the body by the kidneys. Therefore, the risk of side effects or overdose may be greater in patients taking ARBs.
Some antibiotics (e.g., trimethoprim, rifampicin, fluconazole).
Barbiturates. Use of ARBs may increase the depressant effects of these medications.
Over-the-counter (OTC) medications that increase blood pressure. These include (but are not limited to) diet pills and medications used to treat asthma, flu, colds, cough, sinus problems or hay fever.
Grapefruit juice. Grapefruit juice interferes with the liver’s ability to rid the body of some substances. This could lead to a build up of ARBs to toxic levels in the body. The exact nature of this risk is not completely understood, but patients taking ARBs may be advised to refrain from drinking grapefruit juice by their physicians.
Alcohol. Drinking alcoholic beverages could produce a drop in blood pressure. Patients taking ARBs should consult their physician before drinking alcohol.
Lifestyle considerations with ARBs
Angiotensin-II receptor blockers (ARBs) are only one part of a treatment plan for high blood pressure, heart failure or other conditions. That plan usually includes a number of lifestyle changes including weight loss, eating a heart-healthy diet, regular exercise and more. ARBs reduce the symptoms, but do not cure the underlying condition. Therefore, many patients taking ARBs will be on the medication for the rest of their lives, provided no serious side effects occur.
Often, the symptoms that led the patients to seek medical attention will stop once ARBs are introduced. Patients should still continue to take their medication exactly as directed and to keep all scheduled follow-up appointments with their physician.
When first taking ARBs, patients may be advised to avoid driving or operating heavy machinery until they know how the medication will affect them. Patients are more likely to have side effects from ARBs or other antihypertensives if they spend too much time in the heat. Therefore, patients should be certain to drink enough liquids during exercise or in hot weather. Patients may also be directed to take their own blood pressure readings regularly, reporting anything unusual to their physicians.
Patients taking ARBs should inform their physician if they become ill from any cause, especially if severe diarrhea or vomiting occurs. These conditions can cause the body to lose too much water and potassium, leading to low blood pressure (hypotension).
Patients should not stop taking ARBs abruptly unless advised by their physician. Doing so might lead to medical complications.
Pregnant patients should not take ARBs, and women who are or are planning to become pregnant should tell their physicians before taking ARBs.
Pregnancy use issues with ARBs
Women are advised against taking Angiotensin–II receptor blockers (ARBs) during pregnancy, especially during the second and third trimesters. Patients taking ARBs should inform their physician immediately if they become pregnant or are planning to become pregnant, so they can start alternative therapy.
When breastfeeding, some ARBs will pass into breast milk, and the effects of this on the nursing infant are unknown. Therefore, an alternative feeding method is recommended when mothers are taking ARBs.
Symptoms of ARB overdose
Signs and symptoms of overdose can be similar to the medication’s side effects, but are usually more severe. A physician should be called immediately if the patient shows any of the following:
Low blood pressure (hypotension)
Edema (swelling) in the face, mouth, throat, hands or feet
Fainting (syncope)
Dizziness or lightheadedness
Arrhythmias (abnormal heart rhythm) or palpitations
Blurred vision
Chest pain or pressure
Fever, chills or unusual sweating
Child use issues with ARBs
Use of certain most angiotensin-II receptor blockers (ARBs) may not be recommended in children of any age, but especially under 6 years old. Also, because children are more sensitive to the effects of ARBs on blood pressure, they are at higher risk of side effects. Parents are encouraged to discuss the potential risks and benefits with a pediatric cardiologist before their child begins taking ARBs.
Elderly use issues with ARBs
Certain types of angiotensin-II receptor blockers (ARBs) may not be recommended for use in older adults. In general, older adults may be more sensitive to the effects of medications and therefore at higher risk of side effects. Dosages tend to begin on the lower end of acceptable ranges for this population. In addition, elderly patients are more likely to have impaired renal kidney function, which can increase the risk of hyperkalemia (too much potassium in the blood). Therefore, elderly patients may undergo blood or other testing to determine kidney function before being prescribed ARBs.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to angiotensin II receptor blockers:
Are there any other medications that can be used instead of ARBs?
What side effects can I expect from this medication?
Which side effects are serious enough to warrant a trip to the hospital?
How long will I be taking this medication? For life?
What lifestyle changes should I make in conjunction with my medication?
Should I be taking any other medications with the ARB?
What is my target blood pressure?
Is it possible that I can control my blood pressure enough with diet and exercise to someday stop taking medication?
If I miss a dose, what should I do?
Are there any herbs or dietary supplements that will interact with this medication?
