Vasodilators are a fairly large group of drugs that have a vasodilating effect. Peripheral vasodilators dilate small veins and arteries by acting on the smooth muscles of blood vessels. Due to this, venous inflow to the muscle decreases, oxygen deficiency in the myocardium decreases. This group includes medications that affect the distal vessels.
general information
Due to the intake of drugs of this group, blood vessels expand, which reduces both the load on the heart muscle and its oxygen demand. This fact allows you to use them as antianginal agents. Peripheral vasodilators include medications that act on resistive vessels, they are indicated for the treatment of hypertension. This group of drugs was widely used in the last century, and more precisely, in the fifties. Initially, Phentolamine was used to treat heart failure, but it was not widely used due to the large number of adverse reactions.
The use of drugs included in this group should be carried out under the supervision of the attending doctor, since they can significantly reduce blood pressure, and worsen the blood supply to the heart.
Classification
The modern classification of peripheral vasodilators is based on the action of the drug and its place of application:
- The effect on the vessels - mainly on the arterial vessels, "Hydralazine" and "Phentolamine", and on the venous - "Prazosin" and nitrates.
- Alpha adrenergic receptor blockers - Phentolamine, Droperidol, Prazosin, Nifedipine, Hydralazine.
- Inhibitors of the converting enzyme - Enalapril, Captopril. Medications help to convert angiotensin 1 to angiotensin 2, and also act on the smooth muscles of small arteries.
- The direct effect on the smooth muscles of the vessels is Prazosin, Sodium nitroprusside, nitrates.
In addition, peripheral vasodilators are divided into:
- Venous - Molsidomin, Nitroglycerin.
- Arterial - "Hydralazine", "Phentolamine" "Minoxidil".
- Mixed - "Prazosin", "Nifedipine", "Sodium nitroprusside", "Nitroglycerin" and "Molsidomin".
By the speed of the onset of the therapeutic effect:
- Immediate action - "Nitroglycerin", "Corvaton" with intravenous, under the tongue or local external administration.
- Slowed down - "Prazosin", "Isosorbide dinitrate", "Hydralazine".
Indications for use
Venous vasodilators are indicated for overload of the pulmonary circulation, they:
- reduce pressure in a small circle;
- reduce diastolic expansion of the left ventricle;
- reduce the return of venous blood to the heart;
- reduce myocardial oxygen consumption.
Thus, peripheral vasodilators of this subgroup do not increase cardiac output, but only reduce pressure (pressure) in a small circle of blood circulation. Medicines with a predominant effect on small arteries reduce afterload, while they do not affect pressure in a small circle of blood circulation, that is, the level of preload does not change. As a result, the need for myocardium in oxygen decreases, and cardiac output increases. The main side effect of this group of medicines is the occurrence of hypotension and an increase in heart rate. Used in the following conditions:
- "Hydralazine" - with low cardiac output, with severe aortic or mitral regurgitation.
- "Phentolamine" - in case of catecholamine crisis in individuals with pheochromocytoma.
- Dihydropyridines - for the treatment of hypertension.
Medications with a simultaneous effect on venules and arterioles affect the pre- and afterload, so they are prescribed for the treatment of acute heart failure. And such a unique combination as Hydralazine + Isosorbide Dinitrate, used in the treatment of chronic heart failure, within two years of administration helps reduce the risk of mortality.
Pharmacological action of vasodilator drugs
The mechanism of action of peripheral vasodilators is different, this group includes drugs:
- blocking alpha adrenergic receptors;
- calcium ion antagonists;
- affecting smooth myofibrils of arterioles;
- converting enzyme inhibitors.
Despite the different mechanism of action, all drugs affect post- and preload of the myocardium. Pharmacodynamic effects are manifested by a decrease in blood flow to the heart due to an increase in the capacity of the venous part of the vascular bed, and minute volume of blood, due to an increase in the capacity of the arterial component of the autonomic vascular system.
The mechanism of action of drugs with the international nonproprietary name Pentoxifylline
The accumulation of cyclic adenosine monophosphate in the cellular tissue of smooth muscles of blood vessels and in blood cells, as well as the inhibition of phosphodiesterase, is the basis of the mechanism of action of Pentoxifylline, a peripheral vasodilator, the intake of which:
- It improves symptoms in cases of cerebrovascular accident by reducing the overall peripheral resistance and a slight expansion of the coronary vessels. Has a slight vasodilating effect.
- It inhibits the aggregation of red blood cells and platelets, stimulates fibrinolysis, reduces the concentration of fibrinogen in the blood plasma, improving its viscosity.
The drug "Vazonit"
It is a medicine of long (prolonged) action. Pentoxifylline is an active substance that contains 600 mg in one dosage form. Thanks to taking the drug "Vazonit 600":
- in places of blood flow failure, microcirculation improves;
- due to the effect on deformed red blood cells, blood flow improves;
- erythrocyte membrane elasticity increases;
- high blood viscosity decreases;
- platelet adhesion is blocked.
The drug is completely absorbed from the digestive tract. The extended form contributes to the uninterrupted flow of the active substance into the bloodstream. The maximum concentration in the blood is reached after three to four hours and lasts about twelve hours. More than ninety percent of the converted pentoxifylline is excreted by the kidneys.
Indications for the use of drugs with INN pentoxifylline
Doctors recommend "Wazonit 600 ?, as well as other drugs that have the active substance pentoxifylline, in the following conditions:
- Disruption of blood flow, with ischemic origin, acute and chronic.
- Damage to the brain is discirculatory and atherosclerotic.
- Failure of peripheral blood flow, occurring against the background of inflammatory, as well as atherosclerotic and diabetic processes.
- As a symptomatic remedy to cure the consequences that arose after cerebrovascular accident.
- Failure of the middle ear functions of vascular origin, which is accompanied by hearing loss.
- Violation of blood circulation in the vessels of the eye.
- Trophic tissue disorders provoked by a malfunction of venous and arterial microcirculation.
Contraindications and side effects of drugs with the active substance pentoxifylline
According to the instructions for use of "Pentilin" and other drugs that have INN pentoxifylline, they are prohibited for use with:
- Hypersensitivity to pentoxifylline.
- Pregnancy
- Breastfeeding.
- Retinal hemorrhage.
- Heavy bleeding.
- Acute myocardial infarction.
- Under the age of eighteen.
Adverse events may occur from:
- hemostatic system and cardiovascular;
- subcutaneous fat and skin;
- Central nervous system;
- digestive system.
As well as allergic reactions and changes in some laboratory indicators.
The drug "Agapurin Retard"
The active ingredient of this medicine is also pentoxifylline, which in one tablet is 400 mg. After administration, the active substance is gradually released from the dosage form and evenly enters the bloodstream. In addition to improving microcirculation, the drug has an angioprotective effect. Indications for the appointment of a medication are violations:
- blood circulation of the eye;
- cerebral circulation (ischemic);
- functional sharp inner ear;
- venous and peripheral arterial blood flow, provoked by diabetes mellitus, atherosclerosis;
- trophism as a result of varicose ulcerative lesions, frostbite, gangrene;
- peripheral arterial and venous circulation, proceeding against the background of such processes as infectious, diabetic, atherosclerotic.
And also with angioneuropathy and conditions after a stroke, both hemorrhagic and ischemic.
Individuals with diabetes mellitus often require dose adjustment of antidiabetic agents. Otherwise, the risk of hypoglycemia is high. Take the drug twice a day at the same time, it is well tolerated. Adverse reactions are rare.
A drug having INN “Vincamine”
"Vinoxin MV" has a selective vasoregulatory effect on cerebral circulation. Due to the intense oxidation of glucose, it establishes the metabolism of the brain. Oxygen supply to neurons is improving. The peripheral resistance of the vessels of the brain is stabilized. In addition, the drug does not adversely affect the liver and kidneys. Doctors recommend Vinoxin MV to normalize cerebral circulation in case of disorders:
- mental
- concentration of attention;
- memory;
- vision and hearing of vascular origin;
- cranial post-traumatic;
- cerebral (after cerebral ischemia);
- and others.
The duration of the course of treatment and is selected individually by the doctor. Its use is not recommended for pathologies that provoke an increase in intracranial pressure, acute stroke, heart rhythm disturbances, as well as children, pregnant and lactating women. Side effects are minor. Do not increase the dose recommended by the doctor. With prolonged use, monitoring of the liver is necessary.
Peripheral drugs
At present, a large number of drugs with selective action have been developed that are successfully used for the treatment of heart failure, as well as hypertension. The following is a list of vasodilator preparations:
- "Agapurin."
- "Benciclamana Fumarate."
- Duzofarm.
- Complmin.
- Nicergoline.
- The Pentagon.
- Pentoxifylline.
- Pentilin.
- Pentomere.
- "Radomin."
- "Ralofect."
- "Sermion."
- "Furazolidone" and others.
Each drug has a different pharmacological effect. For the successful treatment of pathology, it is important to choose the right tool. In order to avoid unpleasant consequences, before using the medicine, you should read the instructions for use and follow all the recommendations of your doctor.