ACE inhibitors, ARBs and direct renin inhibitors

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ACE inhibitors, ARBs and direct renin inhibitors

Prerequisite basic sciences

Prerequisite basic sciences

Prerequisite basic sciences


ACE inhibitors, ARBs and direct renin inhibitors


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ACE inhibitors, ARBs and direct renin inhibitors

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Candesartan p. 634


Antihypertensives are a class of medication used to treat hypertension, or high blood pressure.

Certain antihypertensives act upon the renin-angiotensin-aldosterone system to decrease blood pressure by inhibiting vasoconstriction and water reabsorption in the kidneys.

Hypertension affects over a billion people around the world, and it’s a major risk factor for heart disease and stroke.

Blood pressure is the force that blood exerts on the walls of blood vessels.

Now, there’s a number of factors that determine blood pressure. For example, imagine a hose connected to a pump where the hose is the blood vessel and the pump is the heart. If more water is pumped out, the pressure in the hose increases.

Now if we squeeze the hose, narrowing the diameter, the pressure inside would be greater and the water will shoot out more strongly. This is similar to how the diameter of the blood vessels can affect blood pressure, which can change in response to different stimuli.

One important mechanism that regulates blood pressure is the Renin-Angiotensin-Aldosterone System - or RAAS for short - which is a cascade of events that ends up increasing blood pressure.

When blood pressure is low, blood flow to the kidneys decreases. The kidneys respond by secreting renin into the bloodstream.

Renin is a proteolytic enzyme that breaks down a protein made in the liver called angiotensinogen, and this gives rise to angiotensin I.

When it reaches the lungs, angiotensin I is converted into angiotensin II by an enzyme called Angiotensin-converting enzyme, or ACE for short.

Now, angio- refers to the blood vessels; and -tens, well it means “to tense.”

So angiotensin II binds to receptors in vascular smooth muscle and causes them to constrict, which increases the blood pressure.

Finally, angiotensin II also stimulates the release of aldosterone by the adrenal glands.


ACE inhibitors, ARBs and direct renin inhibitors are all medications used to treat high blood pressure. ACE or angiotensin-converting enzyme inhibitors work by blocking the enzyme that converts angiotensin I to angiotensin II. This prevents the body from producing too much of the hormone, which can lead to hypertension. ARBs or angiotensin II receptor blockers work by blocking the receptors that angiotensin II binds to constrict blood vessels. This relaxes the blood vessels and lowers blood pressure. Direct renin inhibitors work by inhibiting renin, the enzyme that converts angiotensinogen to angiotensin I, which also reduces blood pressure. All three of these medications can be used alone or in combination with other medications to safely lower blood pressure.


  1. "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
  2. "Rang and Dale's Pharmacology" Elsevier (2019)
  3. "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
  4. "Hurst's the Heart, 14th Edition: Two Volume Set" McGraw-Hill Education / Medical (2017)
  5. "Angiotensin-Converting Enzyme Inhibitors in Hypertension" Journal of the American College of Cardiology (2018)
  6. "ACE inhibitors and ARBs: Managing potassium and renal function" Cleveland Clinic Journal of Medicine (2019)
  7. "ACE inhibitor and ARB therapy: Practical recommendations" Cleveland Clinic Journal of Medicine (2019)

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