Understanding What Drugs Are Angiotensin II Antagonists

October 13, 2025 •

4 min read

Angiotensin II antagonists, commonly known as ARBs, are a class of medications with an excellent tolerability profile, making them a preferred option for treating high blood pressure and other cardiovascular conditions for many patients. These drugs represent a key advancement in managing the renin-angiotensin-aldosterone system, offering a targeted approach to blood pressure regulation.

Quick Summary

Angiotensin II antagonists, or ARBs, block the hormone angiotensin II to relax blood vessels and lower blood pressure. This class of medication includes various drugs that end in "-sartan," used for hypertension, heart failure, and kidney disease.

Key Points

Angiotensin II antagonists (ARBs) block the AT1 receptor: They prevent the hormone angiotensin II from binding to its receptors, leading to vasodilation and reduced blood pressure.
They treat high blood pressure and other conditions: ARBs are commonly prescribed for hypertension, heart failure, diabetic nephropathy, and post-heart attack management.
Examples include drugs ending in '-sartan': The class includes medications such as losartan (Cozaar), valsartan (Diovan), irbesartan (Avapro), and candesartan (Atacand).
ARBs have a lower risk of cough than ACE inhibitors: Their targeted mechanism of action avoids the accumulation of bradykinin, which causes the persistent dry cough seen with ACE inhibitors.
Dizziness is a common side effect: As blood pressure is lowered, patients may experience dizziness or lightheadedness, especially after the first dose.
Pregnancy is a contraindication: ARBs can cause harm to a fetus and should not be taken by pregnant women or those planning to become pregnant.
Pharmacokinetics vary among ARBs: Drugs like telmisartan have a longer half-life, while bioavailability and food interactions differ across the class.

Introduction to Angiotensin II Antagonists

Angiotensin II antagonists, also known as angiotensin II receptor blockers (ARBs), are a class of medications primarily used to manage high blood pressure (hypertension) and treat various cardiovascular and renal conditions. The primary function of these drugs is to counteract the effects of a hormone called angiotensin II, which naturally constricts blood vessels and increases blood pressure. By blocking the binding of angiotensin II to its receptors, ARBs cause blood vessels to relax and widen, allowing blood to flow more freely and reducing the workload on the heart.

Unlike ACE (angiotensin-converting enzyme) inhibitors, which prevent the formation of angiotensin II, ARBs block the receptor where the hormone acts. This targeted mechanism of action leads to a key clinical difference: a significantly lower risk of the dry, persistent cough often associated with ACE inhibitors. This makes ARBs a valuable alternative for patients who cannot tolerate ACE inhibitor therapy.

The Mechanism Behind ARBs

The renin-angiotensin-aldosterone system (RAAS) is a complex hormonal pathway that plays a crucial role in regulating blood pressure. The process begins with the release of renin from the kidneys, which converts angiotensinogen to angiotensin I. Angiotensin-converting enzyme (ACE) then converts angiotensin I into the active hormone, angiotensin II.

Angiotensin II, in turn, has several effects on the body that increase blood pressure:

It acts as a potent vasoconstrictor, narrowing the blood vessels.
It stimulates the release of aldosterone, a hormone that causes the kidneys to retain sodium and water, increasing blood volume.
It promotes the release of vasopressin, another hormone that increases water retention.

Angiotensin II antagonists selectively block the angiotensin II type 1 (AT1) receptors, which are found in the heart, blood vessels, kidneys, and adrenal glands. By preventing angiotensin II from binding to these receptors, ARBs effectively counteract all of these blood-pressure-raising effects. The result is lower blood pressure, reduced fluid retention, and a decreased risk of damage to vital organs over time.

Specific Drugs That Are Angiotensin II Antagonists

The generic names of all angiotensin II antagonists end in the suffix “-sartan.” While they share a common mechanism, each drug has unique pharmacokinetic properties regarding absorption, metabolism, and elimination.

Here is a list of some of the most commonly prescribed ARBs:

Azilsartan (brand name Edarbi)
Candesartan (brand name Atacand)
Eprosartan (brand name Teveten)
Irbesartan (brand name Avapro)
Losartan (brand name Cozaar), one of the most widely used ARBs
Olmesartan (brand name Benicar)
Telmisartan (brand name Micardis)
Valsartan (brand name Diovan)

Indications for Angiotensin II Antagonists

ARBs are used to treat a variety of conditions, with their primary indication being hypertension. However, their benefits extend to other significant cardiovascular and renal diseases.

Hypertension: The main use for ARBs is to lower high blood pressure, either alone or in combination with other medications, such as diuretics.
Heart Failure: They are prescribed for patients with heart failure to help the heart pump more efficiently and reduce the risk of hospitalization.
Diabetic Nephropathy: For patients with diabetes and kidney disease, ARBs can help slow the progression of kidney damage.
Post-Myocardial Infarction: ARBs are sometimes prescribed following a heart attack to reduce the risk of further cardiac events, especially in patients with low ejection fraction.
Stroke Prevention: In some cases, ARBs can be used to lower the risk of stroke in certain individuals.

Important Considerations and Side Effects

ARBs are generally well-tolerated and have a favorable side-effect profile compared to ACE inhibitors. However, as with any medication, they can cause side effects. Common side effects may include dizziness, fatigue, and headache. In rare instances, severe allergic reactions like angioedema (swelling of the face, tongue, or throat) can occur.

Key precautions and interactions include:

Pregnancy: ARBs are strictly contraindicated during pregnancy due to the risk of birth defects and other complications.
Hyperkalemia: Because ARBs can increase potassium levels in the blood, caution is advised when co-administering with potassium-sparing diuretics or potassium supplements.
Drug Interactions: Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen can reduce the blood-pressure-lowering effects of ARBs. Concurrent use should be monitored.
Renal Function: Patients with pre-existing kidney conditions or bilateral renal artery stenosis should be monitored closely, as ARBs can affect renal function.

Comparing Angiotensin II Antagonists

While all ARBs work similarly, their individual pharmacokinetic properties can differ, influencing aspects like dosing frequency and specific interactions.


Drug (Brand Name)	Half-life (approx.)	Bioavailability	Administered As	Comments
Losartan (Cozaar)	6-9 hrs (active metabolite)	~33%	Prodrug	Most commonly prescribed; has a uricosuric (uric acid-lowering) effect.
Valsartan (Diovan)	~6 hrs	~25%	Active drug	Often used for heart failure post-heart attack.
Irbesartan (Avapro)	11-15 hrs	60-80%	Active drug	Longer half-life and higher bioavailability compared to losartan.
Candesartan (Atacand)	~9 hrs	~15%	Prodrug	Converted completely during absorption; higher AT1 receptor affinity.
Telmisartan (Micardis)	~24 hrs	42-58%	Active drug	Longest half-life, supporting 24-hour control.
Olmesartan (Benicar)	N/A	N/A	Prodrug	Effective for hypertension, available in generic form.

Conclusion

Angiotensin II antagonists are a cornerstone of modern cardiovascular therapy, offering effective and well-tolerated treatment for hypertension, heart failure, and diabetic kidney disease. By specifically blocking the AT1 receptors, these "-sartan" drugs provide a targeted approach to reduce blood pressure and prevent associated organ damage. With several options available, each with slightly different properties, a healthcare provider can choose the most appropriate medication for an individual's specific needs and conditions. Given their proven efficacy and safety profile, ARBs have secured a permanent and essential role in pharmacotherapy, particularly as an alternative for patients who cannot tolerate ACE inhibitors. For further information, the British Heart Foundation provides helpful resources on ARBs and related heart conditions.

Authoritative Source

British Heart Foundation: https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/drug-cabinet/arbs

Frequently Asked Questions

The main difference is their mechanism of action. ACE inhibitors prevent the formation of angiotensin II, while ARBs block the binding of angiotensin II to its receptors. This difference means ARBs do not typically cause the dry cough associated with ACE inhibitors.

No, ARBs are contraindicated during pregnancy. They can cause severe birth defects and other complications and should be avoided by women who are pregnant or planning to conceive.

Dizziness is one of the most common side effects, especially after the initial dose. It is caused by the drop in blood pressure.

Angioedema is a rare but serious side effect involving rapid swelling of the face, tongue, and throat. While less common than with ACE inhibitors, it can still occur with ARBs.

While all ARBs have a comparable blood-pressure-lowering effect, their pharmacokinetic properties like bioavailability and duration of action can differ. Some studies suggest longer-acting ARBs like telmisartan may provide better 24-hour blood pressure control.

Yes, NSAIDs can reduce the effectiveness of ARBs, and concurrent use with potassium-sparing diuretics may increase the risk of high potassium levels. It's crucial to inform your doctor and pharmacist of all medications you are taking.

In heart failure, ARBs help the heart pump more efficiently by relaxing blood vessels and reducing blood volume. They are used to manage symptoms and reduce the risk of further heart damage.