What is High blood pressure?

Before getting to know about High blood pressure,  Let us know what is Blood Pressure or BP. It is the pressure exerted on the walls of arteries in the blood vessels. The blood pressure measuring is explained in such a way as systolic BP, the pressure during the contraction of the heart followed by diastolic BP, the pressure during relaxation of the heart. So now the High blood pressure is increased in the flow of blood inside the systemic arteries. It is also termed as Hypertension and is of two types:

• Primary Hypertension 
• Secondary Hypertension

In short, primary hypertension is due to aetiology factors such as family history and secondary hypertension is mainly because of some disease condition in the body.¹

Beta receptors and their role in blood pressure

Adrenergic receptors of our sympathetic nervous system are divided into two types such as

•  ɑ-alpha receptor
•  𝛃- beta receptor

These receptors play an important role in our bodies' excitatory and inhibitory reactions. Because of their structural familiarity, adrenaline, and noradrenaline, often known as catecholamines, activate adrenergic receptors in particular. The activation of beta receptors causes a variety of physiological functions, including positive inotropic (increased heart contraction) and chronotropic effects (increased heart rate), which raise blood pressure in the system. The beta receptors are divided into three types: β1, β2, and β3. Each receptor has a particular function and blocking of beta receptors plays an important role in reducing high blood pressure.

Beta blockers and Blood Pressure

Beta-blockers act by a competitive mechanism with catecholamines and thus bind with beta receptors instead of these hormones and block their action. This leads to inhibition of normal physiological action with the beta receptor, reducing blood pressure. The action of beta blockers in the heart includes negative inotropic effect and bradycardia which is reduced heart rate.²

Types of beta blockers

There are three types of beta blockers namely,

• First generation
• Second generation
• Third generation

The first generation of beta blockers includes

• Propranolol
• Nadolol
• Pindolol        

Second-generation beta blockers are

•  Atenolol
•  Metoprolol
•  Bisoprolol

  The third generation of beta blockers include

• Nebivolol
• Celiprolol
• Carvedilol
• Bucindolo 
• Labetalol

The first generation is nonspecific in action acting on any type of beta receptor followed by the second generation with a specific action in particular types of beta receptors and the third generation is the combination of both types of acting beta blockers.³     

First-generation beta-blockers

The first beta blocker used to treat high blood pressure was propranolol which is a non-selective beta blocker with high lipophilicity and can cross the blood-brain barrier and produce its effect. The drug is well absorbed and it undergoes first-pass metabolism, that is it gets metabolised by the liver and reaches the systemic circulation. Propranolol can reduce systolic and diastolic BP, decrease cardiac output, and reduce blood pressure.²

 Nadolol is another non-selective beta blocker with a long half-life and it is easy to provide an appropriate dosing regimen for this drug. Since it is hydrophilic, it is absorbed in small amounts and is excreted by the kidneys.

Pindolol is also a first generation beta blocker which is mainly used in gestational hypertension in concerns with its safety during pregnancy. It does not produce any effects on uterine tonicity, blood flow, foetal hemodynamics, or foetal heart rate.³  

Second-generation beta blockers

One drug among this type of second-generation beta blocker is atenolol which is a selective β1 receptor blocker with a hydrophilic character and half the amount of the drug gets absorbed in the body. The drug is eliminated in the unchanged form through the kidney. Atenolol was also found to be beneficial for angina patients and it reduces the further attack of angina in these patients. It works by reducing heart rate, and contractile force, and decreasing the oxygen demand of the heart.²

Third-generation beta-blockers

Labetalol and Carvedilol are non-selective beta and alpha receptor antagonists. They are used in the treatment of hypertension and angina pectoris.⁴  Labetalol acts by vasodilation, relaxes the blood vessels, and reduces blood pressure. It has a quick onset of action that produces an immediate effect and a short half-life hence it is used in hypertensive crises in emergencies.³

Contraindications with beta-blockers 

• Beta-blockers are generally contraindicated in people with asthma and reactive airway illnesses because they produce vasoconstriction and exacerbate the condition's severity.
• It must be taken with caution in insulin-dependent diabetes patients since it may hide the symptoms of hypoglycemia and increase glucose intolerance.⁴
• The beta blockers also cause lipid abnormalities by reducing the lipid metabolism in the system.⁵

Summary

• High blood Pressure is a condition with increased blood flow in the systemic arteries.
• Beta-blockers are a type of medication used to treat a variety of conditions including Hypertension.
• There are different types of beta blockers, so it is important to consult a healthcare provider before taking these medications.
• Consult your doctors and pharmacist for precise advice for beta blockers as it is contraindicated in some cases.
• If you feel any discomfort or if you find any abnormal reaction, reach out to the nearby health center immediately.