We welcome you to a comprehensive overview of Alpha Blockers – a group of medications that are known for their wide range of therapeutic uses. In this article, we discuss the pharmacological principles of alpha blockers, their clinical applications, adverse effects, and much more.
Alpha blockers are medications that bind to alpha-adrenergic receptors. These receptors have a crucial role in controlling several physiological processes such as vasoconstriction and vasodilation.
What Are Alpha-blockers?
Alpha-blockers are drugs for circulatory and urinary issues. They’re also known as alpha adrenoreceptor antagonists. In the late twentieth century, prazosin was the first FDA-approved alpha-1 blocker.
The main difference between alpha blockers and commonly prescribed beta blockers is that the former target the heart to ease blood flow. Contrastingly, alpha-blockers act on blood muscles to dilate blood vessels.
Alpha-blockers are antihypertensive drugs. They also can be used for some diseases of the vascular system, prostate, and help in treating some types of tumors. They function by inhibiting certain activities of cells in your nervous system.
How Do They Work?
Alpha-blockers function by partially blocking the pathway through which some cells in your body receive instructions.
They achieve this by inhibiting alpha-receptors, which are present on cells situated at specific locations or organs in the body.
Those receptors inform the cells to contract, constrict or tighten. When those receptors are blocked, those cells remain relaxed. This is due to the fact that a significant number of those cells are lining your blood vessels controlling their width or narrowness, thus, their relaxation helps to lower your blood pressure.
Alpha-blockers are agents that partially suppress the way some of the body’s cells receive orders. By their name, these drugs inhibit alpha receptors.
The role of these receptors is to tell the cells when to contract, compress, or restrict. When these receptors are blocked by alpha blockers, the cells remain relaxed, thus improving blood flow or passing urine.
These drugs act on peripheral vasculature and cause inhibition of catecholamine uptake in smooth muscle and hence lowering of blood pressure due to vasodilation (1).
When Alpha Blockers Are Used
Alpha blockers are rarely the first line of treatment for high blood pressure. Rather, they are used in combination with other drugs including diuretics, when the blood pressure is hard to control.
Sometimes alpha blockers are prescribed for the prevention, treatment or symptomatic relief of an enlarged prostate or benign prostatic hyperplasia.
Side Effects
Low blood pressure and dizziness are the initial signs that you get when you start taking an alpha blocker. This can cause you to faint after sitting or lying down to standing. Therefore, the first dose is usually administered before going to bed.
Other side effects might include:
Dizziness.
Headache.
Fast or pounding heartbeat.
Weakness.
Before starting to use an alpha blocker, tell your health care team about other medicines you are already taking. Alpha blockers may interfere with the activity of some other medications. Do not forget to note if you use beta-blockers, calcium channel blockers or medicines for erectile dysfunction.
Alpha blockers can increase the total cholesterol. However, some studies indicate that prolonged intake of certain alpha blockers may lead to heart failure.
If you have any questions about the drugs you take, ask your health care team.
Types Of Alpha Blockers
Non-selective alpha-1 receptor blockers.
These agents inhibit all alpha-1 receptors without any selectivity.There are three types of alpha receptors: 1A, 1B, and 1D. This subclass is applied in hypertension and BPH. These agents are much more toxic because they can bind receptors in various parts of the body. These are usually administered at bedtime to reduce these side effects.Examples of nonselective alpha-1 receptor blockers include:
Terazosin
Cardura
Cardura XL
Minipress
What Are Some Typical Alpha-blockers?
Alpha-blockers can be selective or nonselective. Selective alpha-blockers act on particular alpha receptors. They may be A1 (A1) receptors or A2 (A2) receptors.
Alpha-1 receptors are present in smooth muscle, skin, eyes, and urinary tract. Alpha-2 receptors are also present in the smooth muscle and locations like the nervous system, blood, pancreas, and fat cells.
Unlike selective alpha-blockers which target specific receptors, nonselective alpha-blockers do not. That is, they inhibit A1 and A2 receptors (2).
Alpha-blockers can either target specific A1 receptors or not. No alpha-blockers that specifically act on A2 receptors have been approved.
Some of the common selective A1 blockers include alfuzosin (Uroxatral), terazosin (Hytrin), tamsulosin (Flomax), doxazosin (Cardura), silodosin (Rapaflo), and prazosin. The nonselective alpha-blockers include phenoxybenzamine (Dibenzyline) and phentolamine (Regitine).
What Diseases Are Covered By Alpha-blockers?
As the name implies, alpha-blockers are alpha-receptor antagonists. They bind to alpha-receptors and maintain their activation of certain cells.
Alpha-blockers have approval from the U.S. Food and Drug Administration to treat the following conditions:
High blood pressure (hypertension)
Alpha-blockers help to reduce high blood pressure through inhibition of the A1 and A2 receptors. Inhibiting that activation allows the blood vessels to relax and reduce blood pressure.
Approved alpha-blockers for high blood pressure include:
– Doxazosin.
– Prazosin.
– Terazosin.
Benign prostatic hyperplasia (BPH)
Benign prostatic hyperplasia, which is also referred to as benign prostatic enlargement, is a condition in which the prostate gland becomes enlarged. When this occurs it may cause difficulty in urination (peeing) because the prostate gland presses on the urethra.
It can also lead to urine retention in your bladder causing bladder stones and infections. It can also cause renal failure in the long run. Alpha-blockers lead to relaxation of your prostate muscle, allowing urine to pass through easily.
Approved alpha-blockers for BPH are:
Prostate gland-specific (these have fewer systemic adverse effects than non-selective).
Alfuzosin.
Doxazosin.
Silodosin.
Tamsulosin (this is non-specific for the prostate gland).
Terazosin.
Pheochromocytomas And Paragangliomas
They are the same tumor type but they have different names due to their location. They may be malignant or benign. These tumors may — but do not necessarily — secrete additional adrenaline and norepinephrine. When you have too much of either in your body, it’s like you’re overdosing on them, with the symptoms to match. Symptoms include headache, sweating, heart complications, and so on. Alpha- blockers prevent the neurotransmitters from having an overdose effect.
Pheochromocytomas (fee-oh-crow-mo-sigh-toe-ma): These develop on your adrenal glands, which are situated above your kidneys.
Paragangliomas (para-gang-lee-oh-mas): These are the tumors that usually develop close to the carotid artery in your neck, but can also develop around the nerves in other parts of your body.
The following drugs have approval for treating pheochromocytomas and paragangliomas:
Phentolamine (can also be useful for diagnosis of these tumors).
Skin and soft tissue treatments
Phentolamine can protect skin areas from the damages that occur due to leakage of norepinephrine out of your blood vessels and into the surrounding tissue. It can also reverse the actions of certain local anesthetics.
Are Alpha Blockers Safe?
Alpha blockers are generally safe. None of them carry a black box warning. No recent recalls on them. They aren’t controlled substances. However, there are some restrictions.
Do not use alpha blockers:
Sensitive to the drug or class.
With strong CYP 3A4 inhibitors
In hepatic impairment (silodosin or alfuzosin)
Use alpha blockers with caution:
In cataract surgery, there is a risk for intra-operative floppy iris syndrome.
In hypotension
Additionally, do not use alpha blockers with other antihypertensive drugs or PDE-5 inhibitors because of the additive hypotensive effects. The PDE-5 inhibitor should be initiated at the lowest dose when the patients are stable on an alpha blocker and vice versa.
Frequently Asked Question :
Alpha blockers are medicines that act on certain receptors in the body. They help treat conditions like high blood pressure and enlarged prostate.
How do alpha blockers work?
Alpha blockers prevent the effects of adrenaline and noradrenaline by binding to alpha-adrenergic receptors. This measure facilitates vasodilation resulting in lowered blood pressure and increased blood flow.
In which medical conditions are alpha blockers used?
Alpha blockers are prescribed for the treatment of several medical conditions such as hypertension, BPH, Raynaud’s disease, and pheochromocytoma.
What are the most frequent side effects of alpha blockers?
Orthostatic hypotension, dizziness, fatigue, and nasal congestion are some common side effects of alpha blockers.
What is the difference between alpha blockers and beta blockers?
Alpha blockers and beta blockers are medicines used for high blood pressure. They work in different ways. Alpha blockers target alpha-adrenergic receptors, while beta blockers focus on beta-adrenergic receptors.
Is it possible to use alpha blockers to treat erectile dysfunction?
Alpha blockers are prescribed for erectile dysfunction, often with benign prostatic hyperplasia. They are sometimes used together.
What precautions should be taken when using alpha blockers?
To avoid orthostatic hypotension, patients taking alpha blockers should avoid sudden changes in posture. Other drugs taken should also be reported to the healthcare providers since alpha blockers interact with other medication.
When do alpha blockers begin to work?
The time to onset of action of alpha blockers is variable based on the medication used and individual response. On the other hand, some individuals may have low blood pressure after about 2 hours of taking the drug.
Are alpha blockers used while pregnant?
Alpha blockers are not recommended during pregnancy unless the potential benefits outweigh the risks. Pregnant women should seek medical advice before taking any medication.
What are some lifestyle changes that can accompany alpha blocker therapy?
Lifestyle changes like diet, exercise, and stress management can improve blood pressure control. Alpha blocker therapy can also help.
I found it fascinating how alpha blockers work to reduce blood pressure by relaxing blood vessels. It would be great to learn more about their side effects and long-term effects on heart health.
I appreciate the detailed breakdown of how alpha blockers function in the body and their effects on blood vessels. It’s fascinating to see how they can help improve blood flow and reduce blood pressure. I wonder if there are any natural alternatives or lifestyle changes that can complement the use of alpha blockers for better heart health?
This article provides a comprehensive overview of the impact of alpha blockers on cardiovascular health. It’s interesting to learn about how these medications work and their potential benefits for individuals with hypertension and other cardiovascular conditions.