Angiotensin II Receptor Antagonist

7/29/2019 Angiotensin II Receptor Antagonist

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Angiotensin II receptorantagonist

The renin-angiotensin system (RAS) orthe renin-angiotensin-aldosterone

system(RAAS) is a hormone system thatregulates blood pressure and water (fluid)

balance.


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When blood volume is low, the kidneys

secrete renin.


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Renin stimulates the production

of angiotensin.


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Angiotensin causes blood vessels to

constrict, resulting in increased blood

pressure.


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Angiotensin also stimulates the secretion

of the hormone aldosteronefrom

the adrenal cortex.


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Aldosterone causes the tubules of the

kidneys to increase the re-absorption of

sodium and water into the blood.


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This increases the volume of fluid in the

body, which also increases blood

pressure.


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If the renin-angiotensin-aldosterone

system is too active, blood pressure will

be too high.


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If the renin-angiotensin-aldosterone

system is too active, blood pressure will

be too high.


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Activation

The system can be activated when there is aloss of blood volume or a drop in blood

pressure (such as in hemorrhage).


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Angiotensin II receptor

antagonist


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If the perfusion of the juxtaglomerularapparatus in the kidney's macula

densa decreases, then the juxtaglomerular cells

release the enzyme renin.


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Renin cleaves a zymogen, an inactive peptide,called angiotensinogen, converting it into angiotensin I.

Angiotensin I is then converted to angiotensinII by angiotensin-converting enzyme (ACE) which is found

mainly in lung capillaries.


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Angiotensin II is the major bioactive product of therenin-angiotensin system, causing these cells to

contract along with the blood vessels surrounding

them and causing the release of aldosterone from

the adrenal cortex.


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Angiotensin II acts asan endocrine, autocrine/paracrine,

and intracrine hormone.


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Their main use is in hypertension (high bloodpressure), diabetic nephropathy (kidney damage

due to diabetes) and congestive heart failure.


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antagonistThese substances are AT1-receptor antagonists

that is, they block the activation of angiotensin II

AT1 receptors.


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antagonistBlockade of AT1 receptors directly

causes vasodilatation, reduces secretion

of vasopressin, reduces production and secretionof aldosterone, amongst other actions the

combined effect of which is reduction of blood

pressure.


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antagonistPressor Inhibition

Valsartan 80 mg 30%

Telmisartan 80 mg 40%Losartan 100 mg 2540%

Irbesartan 150 mg 40%

Irbesartan 300 mg 60%

Olmesartan 20 mg 61%

Olmesartan 40 mg 74%


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antagonistAT1 affinity

Losartan 1000 fold

Telmisartan 3000 foldIrbesartan 8500 fold

Olmesartan 12500 fold

Valsartan 20000 fold


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antagonist

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Angiotensin II Receptor Antagonist