Difference Between Alpha and Beta Blockers

The key difference between alpha and beta blockers is that alpha blockers are drugs that lower blood pressure by preventing the hormone norepinephrine from tightening the smooth muscles in the walls of arteries and veins, while beta blockers are drugs that lower the blood pressure by blocking the effects of hormone epinephrine and reducing the heartbeat rate.

Hypertension is one of the severe diseases in the world currently. To prevent such diseases, the human body needs to have blocking agents that can help arteries and veins in the smooth flow of blood circulation. Alpha and beta blockers are both high blood pressure-reducing medications that are used in clinical setups by clinicians.

CONTENTS

1. Overview and Key Difference
2. What are Alpha Blockers
3. What are Beta Blockers
4. Similarities – Alpha vs Beta Blockers
5. Alpha vs Beta Blockers in Tabular Form
6. Summary – Alpha vs Beta Blockers

What are Alpha Blockers?

Alpha blockers are drugs that lower blood pressure by preventing the hormone norepinephrine from tightening the smooth muscles in the walls of arteries and veins. They are a class of drugs that act on α-adrenergic receptors. Norepinephrine is the agonist for these receptors. These receptors have a common function, such as vasoconstriction. Therefore, alpha blockers prevent such functions upon binding to the receptor. As a result of alpha blockers binding to their receptors, the blood vessels remain open and relaxed. This improves blood flow and reduces blood pressure.

Alpha blockers are of two types: short-acting and long-acting. Short-acting drugs work very quickly, but their effects last for few hours. However, long-acting drugs take longer to work, but their effects last longer. Therefore, the type of alpha blockers depends on patients’ health conditions. Examples of alpha blockers used to treat high blood pressure include doxazosin, prazosin, terazosin, etc. Alpha blockers are not the first treatment choice for high blood pressure. The potential side effects may include dizziness, headache, pounding heartbeat, weakness, etc. Usually, other medications such as diuretics are used when high blood pressure is difficult to control.  Moreover, alpha blockers can treat other diseases such as Raynaud’s disease, benign prostatic hyperplasia and erectile dysfunction as well.

What are Beta Blockers?

Beta blockers are drugs that lower blood pressure by blocking the effects of the hormone epinephrine and reducing the heartbeat rate. They are antagonists of receptors for catecholamines such as epinephrine. These receptors are adrenergic beta receptors of the sympathetic nervous system that mediate fight-or-flight responses. Some beta blockers block the activation of all types of β-adrenergic receptors. Some are selective for one of the three known beta receptors: β1, β2, and β3 receptors. The β1-adrenergic receptors are mainly in the heart and kidney. β2-adrenergic receptor can be found in the lungs, liver, gastrointestinal tract, uterus, vascular smooth muscle, and skeletal muscle. Moreover, β3-adrenergic receptor is present in fat cells.

Beta blockers are predominantly used to treat abnormal heart rhythms and to protect patients from a second heart attack after the first heart attack. Some examples of beta blockers are acebutolol, atenolol, bisoprolol, metoprolol, nadolol, nebivolol, and propranolol. They also have common side effects such as cold hands or feet, fatigue, weight gain, depression, shortness of breath and trouble sleeping, etc.

What are the Similarities Between Alpha and Beta Blockers?

• Alpha and beta blockers both reduce high blood pressure.
• Both are medications.
• They are both antagonists of receptors for catecholamine.
• Both blockers help in dilating blood vessels.

What is the Difference Between Alpha and Beta Blockers?

Alpha blockers lower blood pressure by preventing the hormone norepinephrine from tightening the smooth muscles in the walls of arteries and veins. In contrast, beta blockers lower blood pressure by blocking the effects of the hormone epinephrine and reducing the heartbeat rate. This the key difference between alpha and beta blockers. Furthermore, alpha blockers affect the hormone norepinephrine, while beta blockers affect the hormone epinephrine.

The following infographic presents the difference between alpha and beta blockers in tabular form.

Summary – Alpha vs Beta Blockers

Adrenergic antagonists such as alpha and beta blockers inhibit the function of adrenergic receptors like α-adrenergic receptors and β-adrenergic receptors. Therefore, alpha and beta blockers are both high blood pressure-reducing medications. Alpha blockers are drugs that lower blood pressure by preventing the hormone norepinephrine from tightening the smooth muscles in the walls of arteries and veins. In contrast, beta blockers are drugs that lower blood pressure by blocking the effects of the hormone epinephrine and reducing the heartbeat rate. This is the summary of the difference between alpha and beta blockers.

Reference:

1. Nachawati, Dana. “Alpha Blockers.” StatPearls [Internet] U.S. National Library of Medicine.
2. “Beta blockers.” NHS Choices, NHS.

Image Courtesy:

1. “Alpha-1-blocker-SAR” By Amzker – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Mechanism of action for beta blockers” By Mogsan1 – Own work (CC BY-SA 3.0) via Commons Wikimedia