Alpha Blockers: The Effectual Antihypertensive Drug

Alpha blockers are a group of antihypertensive drugs that aid in hypertension treatment. They have a direct effect on adrenoceptors located in vascular smooth muscle. Alpha blockers became popular in medicine in the middle of the 20th century. Today they are considered indispensable in the treatment of many diseases. Since the late 60s, they are used for high blood pressure treatment and included in the therapeutic regimens.

They have been considered as effective blood pressure-lowering drugs but lost their importance after the discovery of alternative medicines like ACE Inhibitors and Beta Blockers. But by the 90s, alpha-blockers again began to be a popular choice for hypertension.

One of the first drugs in this group was Prazosin. Further, other alpha blockers such as Doxazosin and Terarozin, were launched. All of them, like Prazosin, are used to treat hypertension but differ from it in having a more prolonged action.

What are Alpha Blockers?

Alpha blockers (also known as α blockers or alpha adrenoreceptor antagonists) are a group of drugs that are used to lower blood pressure. Although, they help in hypertension treatment, but not prescribed as first-line medicines for the uncomplicated nature of the disease. They also help in the treatment of urinary problems in men who have an enlarged prostate gland.

Alpha blockers, unlike β-blockers and diuretics, have a positive effect on cholesterol. They help in the removal of harmful cholesterol from the body. They reduce the growth of atherosclerosis substances that reduce blood flow.

Alpha-blockers expand the venous channel and reduce Left ventricular hypertrophy of the walls of the heart’s main pumping chamber. Moreover, they eliminate the risk of coronary artery vasospasm.

Types of Alpha-blockers

Types of Alpha Blockers

There are two main types of alpha-blockers

Selective Alpha Blockers

These drugs block the alpha 1 adrenergic receptor and have a long therapeutic effect. They can reduce vascular activity without increasing the level of norepinephrine (stress hormone), hence prevents rhythm disturbance and shortness of breath. It normalizes the metabolism of fats and carbohydrates.

Although they are more popular as antihypertensive drugs, they also helps in the treatment of prostate gland inflammation and urinary incontinence. These drugs reduce blood pressure without side effects such as arrhythmia, blood sugar spike.

Examples of Selective Alpha 1 Adrenergic Blockers: Doxazosin, Prazosin, and Terazosin. Prazosin belongs to first-generation drugs, whereas doxazosin and terazosin belong to second-generation.

Examples of Alpha 2 Adrenergic Blockers: Atipamezole, Idazoxan, Mirtazapine, and Yohimbine

Non-selective Alpha Blockers

Non-selective hypertension drugs block both alpha 1 and alpha 2 adrenergic receptors. They have hypotensive effects and stabilize the release of norepinephrine. Compared to selective blockers, they have a shorter duration of antihypertensive effect. Therefore, they are not the first choice for hypertension treatment.

Examples of Non-selective Alpha Adrenergic Blockers: Phenoxybenzamine, Phentolamine, Tolazoline, and Trazodone

Note: The use of non-selective drugs is possible only in emergency cases. They are not suitable for continuous use.

When Alpha Blockers Are Used?

The doctor prescribes Alpha blockers for various diseases of the cardiovascular and genitourinary systems. The mechanism of action and effect on the body depends on the selected group of drugs.

A Cardiologist prescribes Selective alpha-blockers in the following cases:

  • High blood pressure
  • Hypertension complications due to metabolic disorders
  • Type 1 and 2 diabetes
  • Benign prostate enlargement.

Non-selective alpha-blockers are commonly prescribed for:

  • Atherosclerosis
  • Pheochromocytoma
  • Blood circulation disorder
  • Endarteritis
  • Withdrawal syndrome
  • Raynaud’s syndrome

Stable therapeutic effects mostly observed after 1-3 months of regular medicine intake. You cannot stop a treatment course without consulting a doctor.

Cardiologist prescribes selective Alpha 1 adrenergic blockers, like Silodosin, for Benign prostatic hyperplasia, painful urination, and high urinary frequency.

Note: Drugs like ACE inhibitors and diuretics are more effective than alpha-blockers in reducing complications related to hypertension. Therefore, the doctor will prescribe it only if other drugs don’t show any positive results.

How Alpha Blockers Work?

Alpha-blockers have a direct effect on adrenergic receptors located in the heart and blood vessel walls. They help stabilize the sympathetic nervous system, improve heart rate, and lower blood pressure.

Alpha-adrenergic blockers dilate blood vessels which improve the blood flow and relieve the heart by eliminating bad cholesterol. Adrenaline and norepinephrine that appear in the smaller arteries and veins can affect the adrenoceptors.

When Adrenaline Interacts with Adrenoreceptors:

  • Blood pressure increases
  • The lumen of blood vessels becomes narrow
  • Blood glucose increases
  • The lumen of the bronchi becomes wider

After taking Alpha-blockers, it has an opposite effect on adrenaline:

  • Dilate blood vessels
  • Lower blood pressure
  • Narrows the lumen of the bronchi
  • Lower glucose levels

Alpha-blockers stop the adrenergic receptor reaction, preventing neurotransmitters from affecting the cardiovascular and other systems. The drug helps to absorb glucose easily, which helps in the fight against diabetes. Due to the blockade of receptors, arrhythmia and heart pain reduces.

You might also be interested in – 101 Most Common Questions About Blood Pressure

Commonly Used Alpha-blockers for Hypertension

Here is a list of alpha blockers recognized as the most popular, safe, and result-oriented.

1) Doxazosin

The use of doxazosin in patients with hypertension leads to a significant decrease in blood pressure. Results are associated with the selective blockade of alpha1-adrenergic receptors located in the vascular walls. Antihypertensive effects of Doxazosin last for 24 hours if taken once a day. During this period, blood pressure decreases gradually.

Doxazosin has a beneficial effect on lipid profile, increasing the ratio of high-density lipoprotein to total cholesterol and significantly lowering the concentration of total triglycerides and total cholesterol. In this regard, it has an advantage over diuretics and beta-blockers, which do not favorably affect these parameters.

Doxazosin decreases the risk of coronary heart disease. Also, it increases insulin sensitivity in patients with impaired glucose tolerance.

Doxazosin has no metabolic side effects and can be used in patients with bronchial asthma, diabetes mellitus, left ventricular failure, and gout. Clinical trials conducted in patients with arterial hypertension, doxazosin treatment was accompanied by an improvement in erectile function. The combined use of doxazosin with PDE-5 inhibitors in some patients can lead to symptomatic arterial hypotension.

2) Terazosin

Terazosin promotes the expansion of blood vessels and thereby reduces high blood pressure. The purpose of Terazosin is to relax the smooth muscles of blood vessels and thereby increase their clearance.

Besides, Terazosin reduces the level of bad cholesterol in the body, normalizes lipid metabolism and urination. It also reduces the load on the heart muscle without causing pronounced tachycardia.

The initial dose of Terazosin is ½ tablet and gradually increases to 2-5 tablets. Pills are taken orally at 1 mg per day. Make sure that the daily dose should not exceed 20 mg. Consult a doctor before taking any medicines.

When using Terazosin in high doses, the patient might face:

  • Painful heart palpitations
  • Low blood pressure
  • Orthostatic hypotension

3) Prazosin

The drug “Prazosin” has a hypotensive effect by dilating the blood vessels and is widely used to treat hypertension and other abnormalities. Prazosin blocks alpha-adrenergic receptors, constricts blood vessels, reduces their peripheral resistance, and lowers blood pressure.

Once you take the medicine, the peripheral veins expand, the load on the heart decreases, and the pressure in the pulmonary circulation improves. The drug can reduce myocardial oxygen demand.

Despite its effectiveness, the drug has side effects and contraindications. Therefore, you should carefully study the instructions for use and consult a specialist.

4) Phentolamine

Phentolamine blocks alpha 1 and alpha 2 adrenergic receptors and hence is commonly prescribed for hypertension. It is also useful in the treatment of endarteritis, Raynaud’s syndrome, pressure sores, and non-healing trophic ulcers. Its active substances quickly restore blood supply to tissues, organs, and skin.

Side Effects of Alpha Blockers

Treatment of high blood pressure using alpha-blockers drugs can cause mild to severe side effects, but not always. Improper intake and overdose are common causes of side effects. Consult your doctor immediately if symptoms become worse.

Regular treatment for side effects includes gastric lavage and intake of sorbents. Do not hesitate and call for emergency assistance to restore health. The side effects do not last long.

Alpha-blocker drugs can cause the following undesirable reactions in the patient:

  • Headache
  • Drowsiness
  • Dizziness
  • Low blood pressure
  • Decreased sex drive

Above is a short list of the side effects associated with alpha-blockers. Each of the many drugs belonging to this pharmacological group has its characteristics, restrictions on the use, possible undesirable reactions. For this reason, a specific medicine for pressure must be prescribed to the patient by a qualified specialist! The doctor will also help you determine the optimal dosage, dosage regimen, and duration of the therapeutic course.

Though Alpha-blockers are commonly used, they should always be taken only after a doctor’s prescription. You must consult the doctor in every step of a regimen.

FAQs

What are alpha blockers used for?

Alpha blockers are commonly used in combination with other drugs to treat hypertension and prostate-related issues in men.

How long do I have to take alpha blockers?

In most of the cases, people have to take hypertensive medicines for life. But in some cases, who have brought their blood pressure under control for more than three years can stop taking the medicines by having a consultation with the doctor. People who follow the right diet and do exercise regularly have better chances to keep their blood pressure under control even without medicines.

Who shouldn’t take alpha blockers?

Doctors categorically forbid patients to take alpha-blocker pills for blood pressure if they have the following health problems:

1) Renal failure proceeding in severe form and stages of decompensation
2) Hypotonia accompanied by low blood pressure
3) Aortic stenosis
4) Heart defects, both congenital and acquired
5) Allergy of a polyvalent nature
6) Heart rhythm disturbance
7) Slow heartbeat (bradycardia)
8) Myocardial contractility
9) Liver failure
10) Asthma
11) Obstructive pulmonary disease in the acute phase
12) Occupational lung disease (pneumoconiosis, etc.)

The use of alpha-blockers for hypertension during pregnancy is categorically contradictory. It can increase the health risks of both the patient and her unborn child.
Medicine narrows the lumen of the bronchi, which can lead to breathing disorders in people with lung disease. Therefore, a doctor supervises the patient closely. It is necessary because of the different responses of each patient.
Children under 18 years old should avoid a-blockers. For diabetic patients, taking these drugs should be accompanied by a constant measurement of blood sugar.

Are alpha blockers safe for pregnant women?

Pregnant women should not take alpha-blockers without a doctor’s consultation. Pregnancy is a condition that requires constant monitoring by a doctor. In the presence of hypertension, the use of alpha-blockers is allowed, but it is necessary to take all precautions. If hypertension was before pregnancy and alpha-blockers were part of the regimen, the doctor might prescribe a replacement.
A similar rule applies during the breastfeeding period. During lactation, the patient must stop the use of this drug or use an artificial way for milk intake.

 

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