Hypertension: Anti-hypertensive medications and their mechanism of action

Hypertension

The heart pumps oxygenated blood in the body through the arteries. Once the oxygenated blood is distributed around the body tissues, it is collected back through the veins. So, the veins carry deoxygenated blood. So, the heart produces a certain amount of blood each time it contracts which is basically known as cardiac output. The cardiac output has a big impact on blood pressure. The cardiac output allows the blood to reach different organs of the body.

Organs are included in the management of blood pressure.

  1. Liver
  2. Lungs
  3. Kidneys
  4. Endocrine organ of the kidneys or the adrenal glands.

When we talk about blood pressure, we are mainly talking and focusing on the pressure by which blood is flowing in the arteries. The arterial pressure can be calculated by Cardiac Output X TPR (Total peripheral resistance). And TPR is the resistance of arteries in this place.

Systolic = When the heart is pumping blood out

Diastolic =When the heart is filling back with blood.

Normal blood pressure 120/80mmHg.

Hypertension means high blood pressure. Unmanaged hypertension can have serious consequences. So, one basic treatment for it is anti-hypertensives.

A – Ace inhibitors, angiotensin receptor blockers, and Alpha-1 receptor blockers

B – Beta Blockers

C – Calcium channel blockers

ACE- Inhibitors

The liver produces angiotensinogen. When there is a decrease in the blood pressure of the arteries the kidneys will detect this and will produce renin. Renin when enters circulation, it is responsible for converting Angiotensin into Angiotensin I. This angiotensin I will then circulate around the body and will get in contact with the membrane-bound enzyme called ACE or Angiotensin-converting enzyme which mainly resides in the lung tissues. Hence, ACE is responsible for converting the enzyme from Angiotensin I to Angiotensin II.

Angiotensin II is an important regulator of blood pressure. Angiotensin II increases blood pressure via a number of mechanisms. Angiotensin II binds to its different types of receptors present in the body which results in Sympathetic activity, vasoconstriction, increase in aldosterone which ultimately results in an increase in blood pressure.

ACE inhibitors or Angiotensin-converting enzymes are the very commonly used Anti-hypertensives. They all end with Prils, for example, Captopril, ramipril.

They stop the activity of ACE which inhibits the conversion of angiotensin I to angiotensin II, which eventually results in a decrease in blood pressure levels.

Side effects include

  • Dry cough
  • Rash
  • Nausea
  • Vomiting
  • Diarrhea
  • Headache

Contraindications for using ACE inhibitors

  • Pregnancy
  • Asthma
  • Chronic cough
  • Allergies
  • Kidney disease (renal stenosis)

Medications with Generic and Brand names;

  • Benazepril (Lotensin)
  • Captopril
  • Enalapril (Vasotec)
  • Fosinopril
  • Lisinopril (Prinivil, Zestril)
  • Moexipril
  • Perindopril
  • Quinapril (Accupril)
  • Ramipril (Altace)
  • Trandolapril

Angiotensin receptor blockers

It blocks the binding of Angiotensin-II to its receptor and thus it will decrease the activity of angiotensin II.

Side effects

  • Headache
  • Nausea
  • Diarrhea
  • Dizziness
  • Backpain

Contraindications

  • Pregnancy
  • Renal stenosis
  • Allergies

When taking ACE inhibitors people suffer from dry cough and then they are switched to Angiotensin receptor blockers.

Medications end with “Sartans”

  • Candesartan (Atacand)
  • Irbesartan (Avapro)
  • Losartan (Cozaar)
  • Olmesartan (Benicar)
  • Telmisartan (Micardis)
  • Valsartan (Diovan)

Alpha-I receptor blocker

They generally work on the vessel epithelial cells. Smooth muscle cells are responsible for the contraction and relaxation of the lumen of blood vessels. When the smooth cells contact and the lumen becomes smaller the blood pressure increase.

Smooth muscle cells have the Alpha-1 receptors.

Nor-adrenaline (Adrenaline, also called epinephrine, is a hormone released by your adrenal glands and some neurons. The adrenal glands are located at the top of each kidney. They are responsible for producing many hormones, including aldosterone, cortisol, adrenaline, and noradrenaline.) binds to the alpha-1 receptor which results in the contraction of smooth muscle cells which will lead to an increase in blood pressure.

Alpha-1 receptor blocks the binding of receptors on the blood vessels. It is a good option for people who have high blood pressure and cholesterol problems.

Side effects: It can lead to Hypotension

  • Doxazosin (Cardura)
  • Prazosin (Minipress)
  • Terazosin

Beta Blockers

They usually end with (-Olol) and Beta receptors are important for sympathetic activity.

The pacemaker cells present in our heart (SA Node) can be affected by Prisympathic and sympathetic nervous system. Endoergic receptors bind with the receptors present on the pacemaker cells which results in an increase in heart rate which results in an increase in cardiac output and hence untimely leads to an increase in blood pressure.

Our heart contains cardiomyocytes which have Beta-1 receptors. So, noradrenaline and adrenaline can stimulate the beta-1 receptors of the cardiac muscle cells to contact stronger and will lead to more powerful contraction. So, a more powerful contraction leads to an increase in cardiac output and hence results in an increase in blood pressure.

So, Betablockers block the beta receptors which will lead to a decrease in cardiac output and a decrease in blood pressure.

Side effects

  • Bradycardia
  • Fatigue
  • Hypotension
  • Decrease in Libido
  • Impotence

Examples.

  • atenolol (also called Tenormin)
  • bisoprolol (also called Cardicor or Emcor)
  • labetalol (also called Trandate)
  • metoprolol (also called Betaloc or Lopresor)
  • propranolol (also called Inderal or Angilol)

Calcium channel blockers

They usually end with (-dipine).

Calcium causes muscle contraction and excitability of muscle in the body. The calcium channel allows and blocks the transportation of calcium in the body which leads to contraction and relaxation of the cardiomyocytes.

  • Amlodipine (Norvasc)
  • Diltiazem (Cardizem, Tiazac, others)
  • Nifedipine (Procardia)
  • Nisoldipine (Sular)
  • Verapamil (Calan SR, Verelan)

Hypertension Diagnosis

  • Diagnosis requires several elevated readings over several weeks (unless > 180/110)
  • BP measurement in both arms
  • Use arm with higher reading for subsequent measurements
  • Ambulatory BP Monitoring
  • For the “white coat” phenomenon, hypotensive or hypertensive episodes, apparent drug resistance

Lifestyle modifications

  • Weight reduction
  • Dietary changes (DASH diet)
  • Limitation of alcohol intake (< 2 drinks/day for men; < 1/day for women)
  • Regular physical activity
  • Avoidance of tobacco use
  • Stress management

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