Angiotensin receptor blockers, known as ARBs, are prescription medications used to manage conditions related to blood pressure and heart function. They work by interfering with a hormonal pathway to relax blood vessels, which lowers blood pressure and makes it easier for the heart to pump blood.
Mechanism of Action
ARBs function within the body’s renin-angiotensin system, which helps regulate blood pressure. When the body senses a drop in blood pressure, the kidneys release an enzyme called renin. This enzyme triggers a chain reaction that leads to the production of the hormone angiotensin II.
Angiotensin II is a potent chemical that causes blood vessels to constrict or narrow. This narrowing increases the pressure within the vessels. Angiotensin II also stimulates the release of another hormone, aldosterone, which causes the body to retain salt and water, further increasing blood volume and pressure.
ARBs work by selectively blocking angiotensin II from binding to its primary sites of action, known as AT1 receptors. These receptors are located on the smooth muscle cells of blood vessels, as well as in the heart and kidneys. By occupying these receptors, ARBs prevent angiotensin II from exerting its constricting effects, which allows blood vessels to relax and widen, directly lowering blood pressure.
The interruption of the angiotensin II signal also has other beneficial effects. It reduces the secretion of aldosterone, which helps the body excrete excess sodium and water, decreasing overall blood volume. This comprehensive action not only lowers blood pressure but also reduces the workload on the heart and helps protect organs from the damaging effects of sustained high pressure.
Conditions Treated by ARBs
Angiotensin receptor blockers are prescribed for several medical conditions, primarily centered around the cardiovascular system. The most common use for ARBs is the management of hypertension, or high blood pressure, which reduces the risks associated with the condition.
ARBs are also a treatment for congestive heart failure. In this condition, the heart muscle is weakened and cannot pump blood efficiently. ARBs help by reducing the strain on the heart, which improves symptoms like shortness of breath and swelling. Following a heart attack, ARBs may be prescribed to help prevent further damage to the heart muscle.
ARBs are also used to protect the kidneys. They are frequently used to treat chronic kidney disease, particularly in individuals who also have diabetes and high blood pressure. These medications can slow the progression of kidney damage by reducing pressure within the kidneys’ filtering units.
Common Angiotensin Receptor Blockers
The specific ARB prescribed depends on an individual’s health profile and the condition being treated. While all ARBs work by blocking the same receptor, they can differ in how the body processes them. The names of these drugs often end in “-sartan,” a helpful identifier for patients.
Frequently prescribed ARBs include:
- Losartan (Cozaar)
- Valsartan (Diovan)
- Irbesartan (Avapro)
- Olmesartan (Benicar)
- Candesartan (Atacand)
- Telmisartan (Micardis)
In some cases, an ARB might be combined with another type of medication, such as a diuretic, into a single pill to manage blood pressure more effectively.
Potential Side Effects
Although many people tolerate angiotensin receptor blockers well, they can cause side effects. The most common is dizziness or lightheadedness, particularly when standing up, as the body adjusts to lower blood pressure. Headaches and fatigue have also been reported by some individuals.
A notable side effect of ARBs is their potential to increase potassium levels in the blood, a condition known as hyperkalemia. High potassium can lead to muscle weakness or irregular heart rhythms. Regular blood tests may be performed to monitor potassium levels, especially in patients with kidney problems or those taking other medications that can also raise potassium.
Less common but more serious side effects can occur. In rare instances, ARBs can cause kidney problems or severe allergic reactions, including swelling of the skin, a condition called angioedema. Some patients taking olmesartan have reported significant digestive issues like severe diarrhea.
Important Patient Considerations
One of the most significant considerations is that ARBs should not be used during pregnancy. These medications can cause harm to a developing fetus, particularly during the second and third trimesters, potentially leading to birth defects or kidney failure in the newborn.
Patients should be aware of potential interactions with other drugs. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen, can reduce the blood pressure-lowering effects of ARBs and may increase the risk of kidney complications. Combining ARBs with potassium supplements or salt substitutes containing potassium can lead to unsafe levels of potassium in the blood.
ARBs are often prescribed as an alternative for patients who cannot tolerate another class of blood pressure drugs called ACE inhibitors, frequently due to a persistent dry cough associated with ACE inhibitor use. While both drug classes affect the renin-angiotensin system, ARBs are less likely to cause this particular side effect.