Angiotensin II receptor blockers (ARBs), formally angiotensin II receptor type 1 (AT₁) antagonists, also known as angiotensin receptor blockers, angiotensin II receptor antagonists, or AT₁ receptor antagonists, are a group of pharmaceuticals that bind to and inhibit the angiotensin II receptor type 1 (AT₁) and thereby block the arteriolar contraction and

sodium retention Hypernatremia, also spelled hypernatraemia, is a high concentration of sodium in the blood. Early symptoms may include a strong feeling of thirst, weakness, nausea, and loss of appetite. Severe symptoms include confusion, muscle twitching, and b ...

effects of renin–angiotensin system. Their main uses are in the treatment of

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...

(high blood pressure), diabetic nephropathy ( kidney damage due to diabetes) and congestive heart failure. They ''selectively'' block the activation of the AT₁ receptor, preventing the binding of

angiotensin II Angiotensin is a peptide hormone that causes vasoconstriction and an increase in blood pressure. It is part of the renin–angiotensin system, which regulates blood pressure. Angiotensin also stimulates the release of aldosterone from the adre ...

compared to ACE inhibitors. ARBs and the similar-attributed ACE inhibitors are both indicated as the first-line

antihypertensive Antihypertensives are a class of drugs that are used to treat hypertension (high blood pressure). Antihypertensive therapy seeks to prevent the complications of high blood pressure, such as stroke and myocardial infarction. Evidence suggests tha ...

s in patients developing

along with left-sided

heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...

. However, ARBs appear to produce less adverse effects compared to ACE inhibitors.

Medical uses

Angiotensin II receptor blockers are used primarily for the treatment of

where the patient is intolerant of

ACE inhibitor Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of hypertension, high blood pressure and heart failure. They work by causing relaxation of blood vessels as well as a decrease i ...

therapy primarily because of persistent and/or dry cough. They do not inhibit the breakdown of bradykinin or other kinins, and are thus only rarely associated with the persistent dry cough and/or angioedema that limit ACE inhibitor therapy. More recently, they have been used for the treatment of

in patients intolerant of ACE inhibitor therapy, in particular candesartan. Irbesartan and losartan have trial data showing benefit in hypertensive patients with type 2 diabetes, and may delay the progression of diabetic nephropathy. A 1998 double-blind study found "that lisinopril improved insulin sensitivity whereas losartan did not affect it." Candesartan is used experimentally in preventive treatment of

migraine Migraine (, ) is a common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few hou ...

. Lisinopril has been found less often effective than candesartan at preventing migraine. The angiotensin II receptor blockers have differing potencies in relation to blood pressure control, with statistically differing effects at the maximal doses. When used in clinical practice, the particular agent used may vary based on the degree of response required. Some of these drugs have a uricosuric effect. In one study after 10 weeks of treatment with an ARB called losartan (Cozaar), 88% of hypertensive males with sexual dysfunction reported improvement in at least one area of sexuality, and overall sexual satisfaction improved from 7.3 to 58.5%. In a study comparing beta-blocker

carvedilol Carvedilol, sold under the brand name Coreg among others, is a medication used to treat high blood pressure, congestive heart failure (CHF), and left ventricular dysfunction in people who are otherwise stable. For high blood pressure, it is gen ...

with

valsartan Valsartan, sold under the brand name Diovan among others, is a medication used to treat high blood pressure, heart failure, and diabetic kidney disease. It belongs to a class of medications referred to as angiotensin II receptor blockers (ARBs) ...

, the angiotensin II receptor blocker not only had no deleterious effect on sexual function, but actually improved it. Other ARBs include candesartan (Atacand), telmisartan (Micardis), and

Valsartan Valsartan, sold under the brand name Diovan among others, is a medication used to treat high blood pressure, heart failure, and diabetic kidney disease. It belongs to a class of medications referred to as angiotensin II receptor blockers (ARBs) ...

(Diovan), fimasartan (Kanarb). Angiotensin II, through AT₁ receptor stimulation, is a major stress hormone and, because (ARBs) block these receptors, in addition to their eliciting anti-hypertensive effects, may be considered for the treatment of stress-related disorders. In 2008, they were reported to have a remarkable negative association with

Alzheimer's disease Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...

(AD). A retrospective analysis of five million patient records with the US Department of Veterans Affairs system found different types of commonly used antihypertensive medications had very different AD outcomes. Those patients taking angiotensin receptor blockers (ARBs) were 35 to 40% less likely to develop AD than those using other antihypertensives.

Adverse effects

This class of drugs is usually well tolerated. Common adverse drug reactions (ADRs) include: dizziness, headache, and/or hyperkalemia. Infrequent ADRs associated with therapy include: first dose orthostatic hypotension, rash, diarrhea, dyspepsia, abnormal liver function, muscle cramp,

myalgia Myalgia (also called muscle pain and muscle ache in layman's terms) is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another likel ...

, back pain, insomnia, decreased hemoglobin levels, renal impairment, pharyngitis, and/or nasal congestion.Rossi S, editor. Australian Medicines Handbook 2006. Adelaide: Australian Medicines Handbook; 2006. A 2014 Cochrane systematic review based on randomized controlled trials reported that when comparing patients taking ACE inhibitors to patients taking ARBs, fewer ARB patients withdrew from the study due to adverse events compared to ACE inhibitor patients. While one of the main rationales for the use of this class is the avoidance of a persistent dry cough and/or angioedema associated with ACE inhibitor therapy, rarely they may still occur. In addition, there is also a small risk of cross-reactivity in patients having experienced angioedema with ACE inhibitor therapy.

Myocardial infarction

The issue of whether angiotensin II receptor antagonists slightly increase the risk of myocardial infarction (MI or heart attack) is currently being investigated. Some studies suggest ARBs can increase the risk of MI. However, other studies have found ARBs do not increase the risk of MI. To date, with no consensus on whether ARBs have a tendency to increase the risk of myocardial infarction, further investigations are underway. Indeed, as a consequence of AT₁ blockade, ARBs increase angiotensin II levels several-fold above baseline by uncoupling a

negative-feedback Negative feedback (or balancing feedback) occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other ...

loop. Increased levels of circulating angiotensin II result in unopposed stimulation of the AT₂ receptors, which are, in addition, upregulated. However, recent data suggest AT₂ receptor stimulation may be less beneficial than previously proposed, and may even be harmful under certain circumstances through mediation of growth promotion, fibrosis, and hypertrophy, as well as eliciting proatherogenic and

proinflammatory Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

effects.

Cancer

A study published in 2010 determined that "...meta-analysis of randomised controlled trials suggests that ARBs are associated with a modestly increased risk of new cancer diagnosis. Given the limited data, it is not possible to draw conclusions about the exact risk of cancer associated with each particular drug. These findings warrant further investigation." A later meta-analysis by the U.S. Food and Drug Administration (FDA) of 31 randomized controlled trials comparing ARBs to other treatment found no evidence of an increased risk of incident (new) cancer, cancer-related death, breast cancer, lung cancer, or prostate cancer in patients receiving ARBs. In 2013, comparative effectiveness research from the United States Department of Veterans Affairs on the experience of more than a million Veterans found no increased risks for either lung cancer(original article
in Journal of Hypertension) or

prostate cancer Prostate cancer is cancer of the prostate. Prostate cancer is the second most common cancerous tumor worldwide and is the fifth leading cause of cancer-related mortality among men. The prostate is a gland in the male reproductive system that sur ...

. The researchers concluded: "In this large nationwide cohort of United States Veterans, we found no evidence to support any concern of increased risk of lung cancer among new users of ARBs compared with nonusers. Our findings were consistent with a protective effect of ARBs." In May 2013, a senior regulator at the Food & Drug Administration, Medical Team Leader Thomas A. Marciniak, revealed publicly that contrary to the FDA's official conclusion that there was no increased cancer risk, after a patient-by-patient examination of the available FDA data he had concluded that there was a lung-cancer risk increase of about 24% in ARB patients, compared with patients taking a placebo or other drugs. One of the criticisms Marciniak made was that the earlier FDA meta-analysis did not count lung carcinomas as cancers. In ten of the eleven studies he examined, Marciniak said that there were more lung cancer cases in the ARB group than the control group. Ellis Unger, chief of the drug-evaluation division that includes Marciniak, was quoted as calling the complaints a "diversion," and saying in an interview, "We have no reason to tell the public anything new." In an article about the dispute, the Wall Street Journal interviewed three other doctors to get their views; one had "no doubt" ARBs increased cancer risk, one was concerned and wanted to see more data, and the third thought there was either no relationship or a hard to detect, low-frequency relationship. A 2016 meta-analysis including 148,334 patients found no significant differences in cancer incidence associated with ARB use.

Kidney failure

Although ARBs have protective effects against developing kidney diseases for patients with diabetes and previous

without administration of ARBs, ARBs may worsen kidney functions such as reducing glomerular filtration rate associated with a rise of serum creatinine in patients with pre-existing proteinuria, renal artery stenosis,

hypertensive nephrosclerosis Hypertensive kidney disease is a medical condition referring to damage to the kidney due to chronic high blood pressure. It manifests as hypertensive nephrosclerosis (sclerosis referring to the stiffening of renal components). It should be distin ...

, polycystic kidney disease,

chronic kidney disease Chronic kidney disease (CKD) is a type of kidney disease in which a gradual loss of kidney function occurs over a period of months to years. Initially generally no symptoms are seen, but later symptoms may include leg swelling, feeling tired, vo ...

interstitial fibrosis An interstitial space or interstice is a space between structures or objects. In particular, interstitial may refer to: Biology * Interstitial cell tumor * Interstitial cell, any cell that lies between other cells * Interstitial collagenase, ...

, focal segmental glomerulosclerosis, or any conditions such as ARBs-treated but still clinically present

that lead to abnormal narrowing of blood vessels to the kidney that interrupts oxygen and nutrient supply to the organ.

History

Structure

Losartan, irbesartan, olmesartan, candesartan,

, fimasartan and

azilsartan Azilsartan is an angiotensin II receptor antagonist used in the treatment of hypertension, developed by Takeda. It is marketed in tablet form under the brand name Edarbi as the prodrug azilsartan medoxomil. The most common adverse reaction in a ...

include the tetrazole group (a ring with four nitrogen and one carbon). Losartan, irbesartan, olmesartan, candesartan, and telmisartan include one or two imidazole groups.

Mechanism of action

These substances are AT₁-receptor antagonists; that is, they block the activation of angiotensin II AT₁ receptors. AT₁ receptors are found in

smooth muscle Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit mus ...

cells of vessels, cortical cells of the adrenal gland, and adrenergic nerve synapses. Blockage of AT₁ receptors directly causes vasodilation, reduces secretion of vasopressin, and reduces production and secretion of

aldosterone Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...

, among other actions. The combined effect reduces blood pressure. The specific efficacy of each ARB within this class depends upon a combination of three

pharmacodynamic Pharmacodynamics (PD) is the study of the biochemical and physiologic effects of drugs (especially pharmaceutical drugs). The effects can include those manifested within animals (including humans), microorganisms, or combinations of organisms (for ...

(PD) and

pharmacokinetic Pharmacokinetics (from Ancient Greek ''pharmakon'' "drug" and ''kinetikos'' "moving, putting in motion"; see chemical kinetics), sometimes abbreviated as PK, is a branch of pharmacology dedicated to determining the fate of substances administered ...

(PK) parameters. Efficacy requires three key PD/PK areas at an effective level; the parameters of the three characteristics will need to be compiled into a table similar to one below, eliminating duplications and arriving at consensus values; the latter are at variance now.

Pressor inhibition

Pressor An antihypotensive agent, also known as a vasopressor agent or simply vasopressor, or pressor, is any substance, whether endogenous or a medication, that tends to raise low blood pressure. Some antihypotensive drugs act as vasoconstrictors to inc ...

inhibition at

trough level In medicine and pharmacology, a trough level or trough concentration (Ctrough) is the concentration reached by a drug immediately before the next dose is administered,Food and Drug Administration (FDA) Package Inserts (PIs) for inhibition of this effect at the 24th hour for the ARBs are as follows: (all doses listed in PI are included) *

80 mg 30% * Telmisartan 80 mg 40% * Losartan 100 mg 25–40% * Irbesartan 150 mg 40% *Irbesartan 300 mg 60% *

Azilsartan Azilsartan is an angiotensin II receptor antagonist used in the treatment of hypertension, developed by Takeda. It is marketed in tablet form under the brand name Edarbi as the prodrug azilsartan medoxomil. The most common adverse reaction in a ...

32 mg 60% * Olmesartan 20 mg 61% *Olmesartan 40 mg 74%

AT₁ affinity vs AT₂

The ratios of AT₁ to AT₂ in binding affinities of the specific ARBs are shown as follows. However, AT₁ affinity vs AT₂ is not a meaningful indicator of blood pressure response. * Losartan – 1000-fold * Telmisartan – 3000-fold * Irbesartan – 8500-fold * Candesartan – greater than 10000-fold * Olmesartan – 12500-fold *

– 30000-fold higher than AT₂ (the ratio of binding affinities of valsartan to AT₁ and AT₂ is 30000:1) * Saprisartan – ???

Binding affinities Ki

Component

Nearly all ARBs contain biphenyltetrazole moiety except telmisartan and

eprosartan Eprosartan is an angiotensin II receptor antagonist used for the treatment of high blood pressure. It is marketed in the United States as ''Teveten'' by Abbvie, the spin-off of the pharmaceutical discovery division of Abbott Laboratories; it i ...

Active agent

Losartan carries a

heterocycle imidazole A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, an ...

while valsartan carries a nonplanar acylated amino acid.

Biological half-life

The third area needed to complete the overall efficacy picture of an ARB is its biological half-life. The half-lives from the U.S. Food and Drug Administration (FDA) package inserts (PIs) are as follows: *

6 hours * Losartan 6–9 hours *

11 hours * Irbesartan 11–15 hours * Olmesartan 13 hours * Telmisartan 24 hours * Fimasartan 7–11 hours

Pharmacokinetics comparison

Analogue-based Drug Discovery (O''ptimizing Antihypertensive Therapy by Angiotensin Receptor Blockers''; Farsang, C., Fisher, J., p.157–167) Editors; Fischer, J., Ganellin, R. Wiley-VCH 2006.

Research

Longevity

Knockout of the Agtr1a gene that encodes AT₁ results in marked prolongation of the life-span of mice by 26% compared to controls. The likely mechanism is reduction of oxidative damage (especially to mitochondria) and overexpression of renal prosurvival genes. The ARBs seem to have the same effect.

Fibrosis regression

ARBs, such as losartan, have been shown to curb or reduce muscular, liver, cardiac, and kidney fibrosis.

Dilated aortic root regression

A 2003 study using candesartan and valsartan demonstrated an ability to regress dilated aortic root size.

Impurities

Nitrosamines

In 2018 and in 2019, the U.S Food and Drug Administration (FDA) found traces of NDMA and NDEA impurities in the angiotensin II receptor blocker (ARB) drug products

, losartan, and irbesartan. The FDA stated "In June 2018, FDA was informed of the presence of an impurity, identified as N-Nitrosodimethylamine (NDMA), from one valsartan API producer. Since then, FDA has determined that other types of

nitrosamine In organic chemistry, nitrosamines (or more formally ''N''-Nitrosamines) are organic compounds with the chemical structure , where R is usually an alkyl group. They feature a nitroso group () bonded to a deprotonated amine. Most nitrosamines are ...

compounds, e.g.,

N-Nitrosodiethylamine ''N''-Nitrosodiethylamine (NDEA) is an organic compound with the formula Et2NNO (Et = C2H5). A member of the nitrosamines, it is a light-sensitive, volatile, clear yellow oil that is soluble in water, lipids, and other organic solvents. It has ...

(NDEA), are present at unacceptable levels in APIs from multiple API producers of valsartan and other drugs in the ARB class." In 2018, the FDA issued guidance to the industry on how to assess and control the impurities. In August 2020, the

European Medicines Agency The European Medicines Agency (EMA) is an agency of the European Union (EU) in charge of the evaluation and supervision of medicinal products. Prior to 2004, it was known as the European Agency for the Evaluation of Medicinal Products or Euro ...

(EMA) provided guidance to marketing authorization holders on how to avoid the presence of nitrosamine impurities in human medicines and asked them to review all chemical and biological human medicines for the possible presence of nitrosamines and to test the products at risk. Text was copied from this source which is © European Medicines Agency. Reproduction is authorized provided the source is acknowledged. In November 2020, the Committee for Medicinal Products for Human Use (CHMP) of the EMA aligned recommendations for limiting nitrosamine impurities in sartan medicines with recommendations it issued for other classes of medicines. The main change concerns the limits for nitrosamines, which previously applied to the active ingredients but now apply instead to the finished products (e.g. tablets). These limits, based on internationally agreed standards (ICH M7(R1)), should ensure that the excess risk of cancer from nitrosamines in any sartan medicines is below 1 in 100,000 for a person taking the medicine for lifelong treatment. Text was copied from this source which is © European Medicines Agency. Reproduction is authorized provided the source is acknowledged. These sartan medicines have a specific ring structure (tetrazole) whose synthesis could potentially lead to the formation of nitrosamine impurities. Other sartan medicines which do not have this ring, such as azilsartan, eprosartan and telmisartan, were not included in this review but are covered by the subsequent review of other medicines.

Azides

In April 2021, the

European Directorate for the Quality of Medicines The European Directorate for the Quality of Medicines & HealthCare (EDQM) is a Directorate of the Council of Europe that traces its origins and statutes to the ''Convention on the Elaboration of a European Pharmacopoeia'' (an international treat ...

(EDQM) warned of the risk of contamination with non-nitrosamine impurities (specifically,

azido In chemistry, azide is a linear, polyatomic anion with the formula and structure . It is the conjugate base of hydrazoic acid . Organic azides are organic compounds with the formula , containing the azide functional group. The dominant applicat ...

compounds) in tetrazole-containing sartans. In September 2021, the EDQM announced that investigations had revealed a novel azido contaminant which occurs only in losartan (losartan azide or losartan azido impurity) and which was found to be mutagenic on Ames testing. Later in 2021 and 2022, several cases of contamination with azido impurities were detected in losartan, irbesartan, and valsartan, prompting regulatory responses ranging from investigation to market withdrawals and precautionary recalls in

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

, Brazil, and Europe (including Switzerland).

Teva Pharmaceuticals Teva Pharmaceutical Industries Ltd. (also known as Teva Pharmaceuticals) is an Israeli multinational pharmaceutical company with headquarters in Tel Aviv, Israel. It specializes primarily in generic drugs, but other business interests include ...

announced that it would change its losartan manufacturing process to prevent future contamination with these impurities, and the Indian API manufacturer IOL Chemicals and Pharmaceuticals applied for a patent on a new synthesis of losartan designed to be free of azido contaminants.

References

External links

* {{DEFAULTSORT:Angiotensin Ii Receptor Blocker