About angiotensin-II receptor blockers
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:
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 failureA 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 diabetesA 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 angiotensin-II receptor blockers (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 angiotensin-II receptor blockers (e.g., losartan) may be prescribed in patients with both LVH and high blood pressure.
Conditions of concern
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.
- Side effects
Potential side effects
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 angiotensin-II receptor blockers 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 angiotensin-II receptor blockers, 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
- 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
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).
- Nonsteroidal anti-inflammatory drugs (NSAIDs).
- 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.
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.
- How to use
Pregnancy use issues
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.
Child use issues
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
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.
Symptoms of medication overdoseA 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
Questions for your doctorPatients 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?