Angiotensin II receptor blockers, commonly known as ARBs, are prescription medications used to manage cardiovascular conditions. Doctors prescribe them to treat high blood pressure and to protect organs like the heart and kidneys.
How Angiotensin II Receptor Blockers Work
The body produces a hormone called angiotensin II that regulates blood pressure. This chemical causes muscles around blood vessels to contract, narrowing the vessels. This constriction increases pressure within the circulatory system, similar to a hose with a narrowed nozzle, resulting in higher overall blood pressure.
ARBs interfere with this mechanism by selectively blocking AT1 receptors, which are sites on the muscle cells of blood vessels. Angiotensin II must bind to these receptors to constrict blood vessels. ARBs prevent this binding from occurring.
This action is like a key being prevented from entering a lock; the ARB molecule occupies the receptor “lock” so the angiotensin II “key” cannot enter. By blocking these receptors, ARBs allow blood vessels to relax and widen in a process called vasodilation. This widening lowers vascular resistance, reducing blood pressure and easing the heart’s workload.
This blockade also has other effects that lower blood pressure. It reduces the secretion of aldosterone, a hormone responsible for sodium and water retention. By preventing angiotensin II from stimulating aldosterone production, ARBs help the body excrete more sodium and water, decreasing the total blood volume the heart must pump.
Medical Applications
The most common reason doctors prescribe ARBs is for managing hypertension, or high blood pressure. As a primary treatment, they lower blood pressure and reduce the associated risks of long-term vascular damage. Controlling blood pressure with ARBs helps prevent more serious cardiovascular events.
These medications are also a treatment for heart failure, a condition where the heart muscle is weakened and cannot pump efficiently. ARBs help by reducing the strain on the heart, decreasing the resistance it must pump against. This can improve symptoms and enhance the function of a failing heart.
Another application is protecting the kidneys, particularly for individuals with chronic kidney disease or kidney damage from diabetes. Angiotensin II contributes to the progression of kidney damage. By blocking its effects, ARBs can slow this deterioration and preserve kidney function.
ARBs are also used for stroke prevention, especially for patients with high blood pressure and left ventricular hypertrophy, an enlargement of the heart’s main pumping chamber. By managing these conditions, ARBs can lower the risk of stroke and heart attack.
Common Types of ARBs
Physicians have several ARB medications to choose from, and the specific drug prescribed depends on the patient’s health and condition. While all ARBs block the same receptor, there are minor differences in how the body processes them. Medications in this class share a common naming pattern, with generic names ending in “-sartan.”
Some of the most widely prescribed ARBs include:
- Losartan (Cozaar)
- Valsartan (Diovan)
- Irbesartan
- Olmesartan
- Candesartan
- Telmisartan
- Azilsartan
Losartan was the first medication of its kind. These are the generic names for the drugs, which are also available under various brand names.
Side Effects and Safety Considerations
Most people tolerate ARBs well, but they can cause side effects. Common issues, especially when starting the medication, include dizziness, lightheadedness, and headache. These symptoms often occur as the body adjusts to lower blood pressure and may improve after a few days. Some individuals may also experience fatigue or nasal congestion.
A less common but more serious side effect is hyperkalemia, an elevated level of potassium in the blood. ARBs can cause potassium levels to rise because they affect how the kidneys handle sodium and potassium. Doctors monitor kidney function and potassium levels with blood tests after a patient starts an ARB. Patients should manage potassium intake from supplements or salt substitutes while taking these medications.
ARBs must not be used during pregnancy, as they can harm a developing fetus. They should not be taken by anyone who is pregnant or planning to become pregnant. Another rare but serious side effect is angioedema, a swelling of the tissues that requires immediate medical attention.
Patients should be aware of potential drug interactions. Taking ARBs with nonsteroidal anti-inflammatory drugs (NSAIDs), like ibuprofen, can reduce the blood pressure-lowering effect and may impact kidney function. Using them with potassium-sparing diuretics or potassium supplements increases the risk of developing high potassium levels.