Alpha adrenergic blockers: what is it, list of drugs, action, classification

Alpha-blockers are drugs of mixed action that can dilate blood vessels, reduce their tone, normalize the movement of blood through the arteries, thereby adjusting the level of pressure.

Unlike beta blockers, many medications of this type do not affect heart rate, which allows their use in a larger number of clinical cases.

However, there are limitations here too, and significant ones. Mixed preparations that have a systemic effect are also presented on the pharmaceutical market.

The selection of a specific medication and regimen for its use is the prerogative of a cardiologist after a thorough in-person diagnosis.

In this case, a change in the method of use is likely; during dynamic observation, ineffectiveness or poor tolerability may be revealed. The problem is complex and cannot be solved on your own.

Mechanism of action

There are four types of adrenaline receptors in the body: beta-1,2 and alpha-1,2.

All of them react in one way or another to an increase in the concentration of a certain substance, perceiving this factor as a signal for narrowing of the arteries, an increase in pressure, and the mobilization of the body for fight and physical activity.

This natural mechanism was inherited by humans from distant ancestors and has “wild” roots.

• Alpha 1 adrenergic receptors are located in arterioles, ensure their spasm, increase blood pressure and reduce the lumen of blood vessels.
• Alpha 2 adrenergic receptors, on the contrary, dilate blood vessels and reduce blood pressure.

Alpha blockers have a complex effect on cardiovascular structures, creating several beneficial effects at once:

• Dilation of blood vessels of all sizes. The work of the drug on the peripheral circulatory system is especially noticeable, which significantly improves microcirculation in the limbs, heart, and brain.

However, the main effect of this action is a decrease in blood pressure due to an additional decrease in vascular tone (their dilation).

Resistance drops, liquid tissue moves through the system without problems.

• Normalization of metabolic processes in the heart, in parallel, alpha-blocker drugs reduce the myocardium's need for oxygen.

This is an important point, because medications in this case are allowed to be used in patients with heart failure, including the elderly and others, when treatment with beta blockers is not possible.

• Normalization of carbohydrate metabolism. The effect is not directly related to cardiac pathologies.

Its essence lies in the ability to reduce insulin resistance, tissues become more sensitive to its influence, and better absorption of glucose begins.

Therefore, alpha-blockers as an additional remedy, especially with a parallel course of cardiovascular abnormalities, are prescribed to diabetics (regardless of what form of the disease is present, 1 or 2).

• Restoration of lipid metabolism. The drugs are able to inhibit the absorption of “bad” cholesterol without affecting cholesterol (the so-called high-density lipoproteins). Also, alpha-blockers can prevent the formation of cholesterol plaques. Therefore, medications are allowed and recommended for use in atherosclerosis, as an additional remedy for eliminating fat metabolism disorders.
• Relieving swelling and inflammation. The effect has nothing to do with the cardiovascular system, and not all alpha receptor blockers have it to the same extent. However, this action made the medications in demand in urological practice. Due to the ability to relax the bladder neck and facilitate the passage of urine, some names are actively used for complex therapy of prostatitis and benign glandular hyperplasia (adenoma) as a symptomatic remedy.

We are talking only about alpha-2 adrenergic blockers. The names affecting type 1 have some differences.

Thus, most of them increase blood pressure and provoke stenosis (narrowing) of blood vessels, therefore they are not used in cardiological practice (with the exception of only a few medications).

Such drugs are used in a narrow field, as part of the treatment of erectile dysfunction and some other conditions.

Features of application

Despite the lack of influence of the drugs on the mental state and reaction rate, strict adherence to the indicated dosage is still required, otherwise an overdose may occur.

In some groups of patients, a positive effect does not occur after using a certain dose of the drug, then, with the consent of the doctor, the dosage is increased. The recommendation applies to medications with a course of treatment of 1 week or more.

A-blockers reduce cholesterol levels and increase lipoproteins. The drugs block the unwanted effects of thiazide diuretics. Because of the listed properties, the product is actively used in sports.

Today, long-acting drugs have been developed that provide short-term positive effects with a single use. Such drugs are indicated for use to relieve attacks and prevent complications.

Classification

Typification is carried out for several reasons. The mechanism of operation can be considered key.

Accordingly, they distinguish: blockers of alpha-1, alpha-2 adrenaline receptors and mixed medications that affect alpha-1 and 2 at the same time.

Another classification is also used. It is based on the selectivity of the use of medications.

Cardioselective (alpha-1) do not affect the heart rate, reduce blood pressure, normalize metabolic processes, tissue trophism, and have the ability to restore blood flow.

Non-selective ones act simultaneously on all alpha type receptors (both 1 and 2), therefore they can reduce the heart rate, which is not always desirable.

Alpha-1 receptor blockers (selective)

Medicines are widely used in cardiology practice, treatment of impotence, and sexual incompetence in men.

Additional indications include benign prostatic hyperplasia, septic and non-infectious inflammation of the prostate, and impaired urine outflow.

The general actions of all medications in this subgroup can be represented in a small list:

• Relaxation of the muscles of the prostatic part of the urethra, the neck of the bladder and, accordingly, with the disappearance of spasm, the discharge of urine is normalized.
• Normalization of blood flow in the pelvic area. Due to this, the cavernous bodies are better filled and potency is restored in a relatively short time.

Urapidil

The newest, most effective and safe drug alpha-1 adrenergic blocker of peripheral and central action, trade name Ebrantil.

The main task of the medication is to combat severe resistant forms of hypertension and symptomatic increases in blood pressure. Also crises.

Oddly enough, there are no serious reasons for refusing to use it. It does not provoke an acute hypotensive reaction and reflex tachycardia (caused by vasodilation).

Urapidil is not approved for use in children or pregnant women. Also, if there are other diseases of the cardiac structures, it is worth starting therapy with small doses, otherwise there are no grounds for refusal.

Side effects, according to research, are relatively common, but they are also easily tolerated, which makes Urapidil a medication that can be prescribed for a course and even long-term use.

Prazosin

Used for the treatment of mixed cardio-profile conditions. Mainly to eliminate arterial hypertension and symptomatic rise in blood pressure.

Also congestive heart failure, regardless of the phase of its course.

It has a selective effect, selectively affecting some receptors, leaving others untouched.

Tamsulosin

It is not suitable for the treatment of cardiac diseases, because it has the ability to influence the vascular muscles to a small extent, as a result of which an increase in blood pressure is observed.

The name has become widespread in urology, as a means for the symptomatic correction of benign prostatic hyperplasia and prostatitis.

The medicine is included in the list of vitally important medications. It should not and cannot be used independently due to the abundance of contraindications and side effects.

Doctors strictly monitor tolerability in order to adjust the dosage, or even the course itself.

Silodosin

Trade name Urorek. It has a similar pharmacological effect to Tamsulosin, but is more gentle.

There are slightly fewer contraindications, which allows the drug to be used by a larger number of patients.

As in the previous case, use in the treatment of cardiovascular diseases is not recommended. There is no point in this.

The complete list of alpha-1 adrenergic blockers is presented in the table:

Possible side effects from taking

Beta blockers for hypertension are vital because they reduce the risk of complications of this disease. Cardioselective drugs are quite well tolerated. In only a small proportion of patients they can cause:

• cardiac disorders: slow pulse, decreased blood pressure less than 100/60 mmHg. Art., slowdown of A-B conduction, the appearance of shortness of breath, weakness;

• at the beginning of treatment, dry mouth, nausea, stool disorders are possible, changes in liver function are rare;

• in the first weeks of therapy, fatigue, weakness, dizziness, headache, a feeling of chilliness in the extremities, and impaired sensitivity are likely to occur; runny nose, lacrimation or dry eyes, insomnia and depression are not excluded;

• in people with diabetes, an excessive dosage of selective beta blockers can lead to a decrease in blood glucose levels;

• with asthma, its course is likely to worsen;

• Allergic manifestations (urticaria) cannot be excluded;

• Some observations demonstrated a decrease in platelet count and bleeding.

Possible undesirable effects of AAB:

• sometimes – hypotension when getting out of bed, so they need to be prescribed at night;

• drowsiness, weakness, dizziness;

• nasal congestion.

Any unusual symptoms that occur due to the use of these drugs should be reported to your doctor. Some of them require only a change in dose or dosage regimen without the need for discontinuation. If the drug needs to be discontinued, this should be done gradually, reducing the dose over several days. Sudden cessation of beta blockers can cause withdrawal syndrome - a sharp increase in blood pressure and increased heart rate.

We recommend reading about arterial hypertension in old age. You will learn about the features of arterial hypertension in this age group, the rules for measuring blood pressure, risk factors for hypertension, and methods of normalization. And here is more information about the treatment of diabetes and hypertension.

Alpha-2 blockers

They are not used for the treatment of cardiological diseases, since they have very little effect on the vessels of internal organs.

The only representative of the group is Yohimbine. This is a dietary supplement (BAA) that improves erectile function.

Selectively blocks central and peripheral presynaptic and postsynaptic (in large doses) alpha2-adrenergic receptors.

Has a stimulating effect on the central nervous system. Increases sexual desire, strengthens erection, normalizes potency.

The drug is prescribed with caution when taking medications in parallel to normalize blood pressure.

The main effect may be enhanced with a sharp drop in vital signs.

Alpha-1-2 blockers (non-selective)

They dilate blood vessels of all sizes, reduce their total peripheral resistance and the load on the heart.

Reduce the risk of sudden cardiac death by 20-50% in people suffering from coronary artery disease or heart failure.

Reduce the frequency of angina attacks and improve exercise tolerance. In the treatment of hypertension, they reduce the risk of developing coronary artery disease, heart attack and stroke.

Mixed medications

They have combined properties: they simultaneously block both alpha and beta adrenergic receptors. There are many names, there is no fundamental difference between them.

Some have a greater effect on the cardiac component, others on the vascular component. The selection of the drug is carried out by a cardiologist through tests, therefore it is recommended to prescribe a course in a hospital.

This way, the risks will be lower, the response rate will be higher, which will allow you to select treatment in a short time and normalize the patient’s condition.

Further, minor corrections are possible as part of regular follow-up examinations on an outpatient basis.

Mixed alpha-beta blockers

Alpha-beta adrenergic blocking drugs of mixed type have a blocking effect on both alpha and beta receptors. These include:

• Trandol;
• Carvetrend;
• Amipress;
• Recardium;
• Karvedigamma;
• Abetol;
• Talliton;
• Coriol;
• Labetol;
• Vedicardol;
• Credex;
• Acridilol;
• Carvenal;
• Dilatrend.

Some of the drugs listed above affect blood pressure and blood vessels, while others affect the heart. A qualified specialist should select a drug, its optimal dosage and duration of the therapeutic course, taking into account all the features of a particular clinical case!

Indications

In all cases the reasons for application will not be the same. But several groups can be distinguished.

As part of the normalization of cardiac activity:

• Arterial hypertension, regardless of type. Including a symptomatic increase in tonometer readings. It is used for long-term effects, like most drugs of this type, or for urgent relief within an emergency condition.
• Heart failure of various forms. In all cases. A characteristic feature of alpha-blocker drugs is their ability to reduce the need for oxygen in cardiac structures. There is also a restoration of metabolic processes.
• Emergency conditions such as hypertensive crises, myocardial infarction. By what symptoms can you recognize a pre-infarction state, read here.

Noncardiac indications:

• Benign prostatic hyperplasia. Previously, it was called prostate adenoma.

It is accompanied by the growth of this small organ with compression of the urethral canal and disruption of the normal outflow of urine.

The situation is aggravated by the development of a reflex spasm of the bladder neck. Alpha blockers are prescribed to relieve symptoms.

• Prostatitis. Inflammatory pathology. However, contrary to the ideas of Russian medical science, only 10% of the situation is of infectious origin.

Drugs are used to eliminate the symptomatic component in this case.

It will not be possible to radically influence the situation. Surgical treatment is necessary. And then the doctors are trying to delay this moment.

Contraindications

The reasons for refusing to use them are quite few, despite the seriousness of these drugs.

• Excessive decrease in blood pressure levels. Hypotension. Regardless of the origin of this condition.
• Breastfeeding period, pregnancy at any stage. The use of the products is strictly prohibited due to the ability to harm the mother and child.
• Intolerance to the components of a particular pharmaceutical product.
• Multiple immune responses to medications. The so-called polyvalent allergy. It is rare and is not considered an absolute contraindication. It is necessary to carefully monitor the patient's condition.
• Severe kidney dysfunction. Decompensation.
• Heart defects, congenital and acquired, associated with impaired myocardial contractility, nutritional disorder of cardiac structures.
• Also vascular anomalies such as aortic stenosis and others.
• Bradycardia. Reduced heart rate. Many medications from the group of adrenaline receptor blockers can affect heart rate downward. If the rhythm is disrupted, this can be deadly.

Side effects and overdose

Like all medicines, adrenergic blockers sometimes cause unwanted effects, such as:

• dizziness;
• a sharp decrease in pressure;
• collapse;
• headache;
• nausea or vomiting;
• rapid pulse;
• lack of air;
• allergic reactions;
• frequent urination.

Side effects do not always occur. They often occur due to improper use or overdose of medication. Any reaction to the drug should not be ignored. Contact your doctor if you notice any symptom that makes you feel worse.

Since this pharmacological group includes many different drugs, the symptoms of overdose are different. Intoxication often occurs, which is manifested by headache, vomiting, trembling of the limbs, respiratory depression, and a strong decrease in blood pressure. Treatment includes gastric lavage, sorbents and antagonists. Do not hesitate and call emergency help to restore your health.