The overall effect of all drugs in the group is based on the ability to increase the strength of myocardial contractions, resulting in increased cardiac output and stroke volume. Cardiotonic drugs reduce diastolic volume, pulmonary and systemic pressure in the veins, as well as pressure when filling the ventricles.
- Cardiac glycosides – “Strofantin”, “Korglikon”, “Digoxin”.
- Adrenergic drugs – Isadrin, Dobutamine, Dopamine.
- Nonadrenergic synthetic drugs – Amrinon, Milrinon.
The choice of drugs used is associated with the severity of the patient’s condition and the form of the course of the disease.
Sources of obtaining compounds with cardiotonic properties are medicinal plants from certain families. They are well studied by a science called pharmacognosy. The names of the drugs come from the plants from which they are isolated. For instance:
- red (purple) type of digitalis (digitalis) – Digitaloxin, Cordigitum;
- woolly type of digitalis – Digoxin, Celanide, Lantozide;
- rusty digitalis – Digalen-neo;
- adonis (Campion) – Adoniside;
- strophanthus – Strofantin K, Strofantidin acetate;
- lily of the valley – Korglikon;
- icteric – Cardiovalen.
From a chemical point of view, cardiac glycosides are a combination of the following substances:
- Aglycon (genin) is a steroid structure similar in chemical structure to hormones, bile acids, sterols. It is genin that determines the magnitude and mechanism of the cardiotonic action of the drug.
- Sugar part (glycon) – can be represented by molecules of different sugars, it is responsible for the ability to dissolve and be fixed in tissues.
The duration of action and characteristics of the administration of these drugs depend on the chemical formula. Their classification is also based on this. Among cardiac glycosides, there are drugs that are better soluble in fats (Digoxin, Digitoxin, Celanide). They are well absorbed in the intestines and poorly excreted in the urine, therefore, are prescribed for oral administration.
On the contrary, agents that are highly soluble in water are poorly absorbed in the digestive tract, so they are best administered parenterally (Korglikon, Strofantin). They are well excreted through the kidneys, the duration of their action is small.
The duration of glycosides is also affected by their ability to form bonds with blood plasma proteins and accumulate. The longest running Digitoxin (up to 2-3 weeks), the least Strofantin and Korglikon (2-3 days). Digoxin and Celanide have an average duration of action (average week).
The group is represented by herbal or synthetic products. Preparations based on plant substances were obtained from digitalis, adonis, spring lily of the valley, oleander, strophanthus, etc.
The duration of the therapeutic effect, the effect of accumulation in the body, and the neurotoxicity of drugs completely depend on their ability to form complexes with blood plasma proteins. The stronger the bond, the higher the efficiency of the glycoside. Cardiotonic agents of this group have an effect based on the following mechanisms:
- there is a shortening of systole with its simultaneous strengthening;
- the resting period of the heart muscle lengthens;
- heart rate decreases;
- increased ability of the myocardial muscle to arousal;
- with an overdose of drugs, ventricular arrhythmia develops.
Methods of Use
Cardiac glycosides have two types of pharmacological effects:
- Cardiac – an increase in contractile activity of the myocardium, a decrease in conduction and heart rate (HR), an increase in the excitability of the heart muscle. In addition, they contribute to an increase in the duration of diastole – the period when the heart rests and accumulates energy reserves.
- Extracardial phenomena – narrowing of peripheral vessels, diuretic and sedative effect.
The implementation of the main mechanism of action of cardiac glycosides (an increase in the strength of systolic contractions) leads to an increase in indicators such as stroke and minute blood volume, to a decrease in the anatomical size of the heart, lower venous pressure, and elimination of edematous syndrome. It is important that the oxygen consumption of the myocardium does not increase.
The drugs of this group equally increase myocardial contractility both in the presence and in the absence of signs of functional heart failure. But in healthy people there is no increase in minute release. The degree of exposure depends not only on the dose of the drug, but also on the individual sensitivity of the body of a particular person.
Due to the high risk of side effects and the presence of contraindications for use, the group of cardiac glycosides is a potentially dangerous drug, so only a specialist can treat them.
The following pathological conditions become indications for the appointment of cardiac glycosides:
- heart failure – acute and chronic;
- supraventricular arrhythmias (tachycardia), including with a paroxysmal course;
- atrial fibrillation;
- atrial fibrillation attacks;
- pericardial tamponade of the heart (compression).
Contraindications for the appointment of these drugs:
- Cardiac glycosides can not be treated with bradycardia, atrioventricular blockade of varying degrees, unstable angina.
- It is forbidden to prescribe these drugs during acute inflammatory processes (myocarditis), in fainting conditions caused by heart rhythm disturbances (attacks of Morgagni-Adams-Stokes).
- An absolute contraindication is a history of intolerance to digitalis and other cardiotonic plants.
- You can not continue treatment with cardiac glycosides with severe symptoms of intoxication.
Immediately it is worth warning about the impossibility of self-treatment with these drugs: due to toxicity, doses should be selected by the attending physician individually, so that dangerous side effects do not appear.
What are the principles of cardiotonic therapy for heart failure? There are two types of saturation of the body with cardiac glycosides:
- fast digitalization – maximum loading doses are prescribed from the very beginning with the subsequent transition to a maintenance regimen;
- slow digitalization – the use of maintenance dosages from the first day of treatment.
The first method is used in a hospital with the monitoring of possible toxic reactions. The second method involves the use of a specific cardiac glycoside for the treatment of chronic heart failure at home. There are special formulas for calculating the dose of the drug, nomograms for determining the magnitude of the loading and supporting doses, depending on the patient’s body weight, the state of renal functions (creatinine level), and the risk of adverse reactions.
Glycoside intoxication – what is it? It manifests itself in the form of changes from different organs and systems, namely the gastrointestinal tract, central nervous system, organs of vision, and heart.
- abdominal cramps, vomiting, loss of appetite;
- headaches, lethargy, sleep disturbance, restless behavior, hallucinations up to
- confusion, etc .;
- loss of visual fields, disorders of color perception, etc.
- heart rhythm disturbances – extrasystoles, ventricular arrhythmias, blockades and other types.
Options for measures to eliminate intoxication from cardiac glycosides are:
- Drug withdrawal, ECG monitoring in dynamics with subsequent dose adjustment – in the event of the occurrence of single extrasystoles or degree 1 blockade without cardiac output disturbances.
- Withdrawal of the drug and the appointment of antiarrhythmic drugs inside (potassium chloride, magnesium orotate, Panangin) or parenterally (lidocaine, Amiodarone, Unitiol).
In the absence of the effect of antiarrhythmic drugs, defibrillation is used. If the heart rate is too rare, an artificial pacemaker (pacemaker) is installed. To prevent intoxication with drugs such as cardiac glycosides, maintenance doses of drugs should be carefully selected and potassium losses replaced in a timely manner.
It is a short-acting cardiac glycoside used in case of acute form of insufficiency. “Strophanthin” does not tend to accumulate in the body. The drug enhances the contractile function of the myocardium and increases the minute volume of blood. In parallel, there is a reduction in the size of the heart muscle and a decrease in its oxygen demand.
It is used intravenously, intramuscularly, in some cases – inside. Taking large amounts can lead to an overdose. Application with other drugs changes the effectiveness of the action of glycoside:
- with barbiturates, the effect is reduced;
- with “Reserpine”, sympathomimetics and antidepressants can cause the development of cardiac arrhythmias;
- reception with tetracyclines, “Levomycetinum”, “Amiodarone” and “Captopril” strengthens cardiotonic action;
- magnesium sulfate contributes to the development of cardiac atrioventricular block.
Characterization of drugs
Non-glycoside cardiotonic agents with a short-term effect. The group is used in acute heart failure to support important body functions.
“Isadrin” is a stimulant of adrenergic receptors of blood vessels, bronchi and the heart. The drug has a hypotensive effect, strengthens the contractility of the heart muscle. It is used in cardiac surgery with a sharp decrease in contractility during surgery, as well as in cardiogenic shock. Reviews of doctors warn: improper use or oversizing can cause fibrillation of the ventricles of the heart.
“Dobutamine” is a cardiotonic agent of a non-glycosidic structure, which has a stimulating effect on the heart muscle, and also normalizes coronary blood flow. The risk of developing arrhythmias when using this agent is quite low, since Dobutamine has practically no effect on cardiac automatism.
It is prescribed, if necessary, to strengthen the contractility of the myocardium. In some cases, it can cause the development of side effects:
- increased heart rate;
- pain behind the sternum.
“Dopamine” is a catecholamine that stimulates adrenergic receptors. The drug increases blood pressure, enhances coronary blood flow. It is prescribed for acute myocardial failure, shock. Caution should be used for myocardial infarction, pregnancy, thyroid disease, arrhythmias.
These are cardiotonic agents used in case of acute coronary insufficiency. The drugs act on the contractility of the heart muscle, strengthening it. They can provoke the development of arrhythmia and a decrease in blood pressure, impaired renal function.
Cardiotonic drugs of this group can not be used for heart defects, as well as cardiomyopathy, heart rhythm disturbance, aortic aneurysm, kidney failure, heart attack and during the period of gestation.
Amrinon is used exclusively in intensive care units, so that the patient is constantly under the control of special devices that signal his condition. In addition to strengthening heart contractions, the drug dilates blood vessels, increases blood flow during systole, and reduces pulmonary pressure.
Available in the form of a solution. For intravenous administration, it is diluted exclusively in physiological solution of sodium chloride. Do not mix with other medications. With the introduction of a possible sharp decrease in pressure, increased heart rate, arrhythmia, the appearance of headache, gastrointestinal disorders.
Milrinon is more active than the first representative of the group, and according to reviews it is better tolerated by patients. The use of the drug in pregnancy and the development of myocardial infarction is contraindicated. It belongs to the drugs of group A. The need for the use of the drug is determined solely by the doctor.
Modern pharmacology presents in a wide assortment of medicines called cardiac glycosides, the list of the most popular of them looks like this:
- Digitoxin is the longest acting drug, it is almost completely absorbed in the small intestine, its plasma concentration is 18-20 times higher than after taking the same dosage of Digoxin. This agent almost completely binds to plasma albumin, therefore, it has high cumulation (accumulation). Digitoxin begins to act approximately half an hour or an hour after intravenous administration, 4 hours after ingestion. The elimination half-life is on average 5 days and does not depend on impaired renal function. With the slow method of digitalization, stabilization of the therapeutic level of the drug is achieved after 3 or 4 weeks.
- Digoxin (Acedoxin) – This cardiac glycoside is well absorbed in the intestines, but it only binds to plasma proteins by a quarter. Its half-life is about 2 days, about a third of the dose taken is daily output. Excreted in the urine almost completely unchanged, at a speed depending on the presence of impaired renal function. After intravenous administration, the action begins on average after 20 minutes, and after oral administration after a couple of hours. The individual sensitivity of individual patients to this drug was noted, and tolerance of large doses is better in young children compared with adults. With a single use of this glycoside, muscle mass is always taken into account, and not the total body weight, since there is practically no accumulation in adipose tissue. Slow digitalization leads to a stable concentration of the drug after about a week.
- Celanide (Lanatoside) – similar in chemical formula to Digoxin, these cardiac glycosides have similar pharmacodynamic properties. However, Celanide is less absorbed in the intestine after oral administration, intravenous administration allows it to begin to act earlier than Digoxin.
- Strofantin K is a water-soluble glycoside that is rapidly excreted through the kidneys, cannot accumulate in the body, and is used exclusively for parenteral administration. This tool does not greatly affect heart rate and pulse conduction in the myocardium. When using the fast saturation method, it begins to act a couple of minutes after entering the blood, reaching a maximum in half an hour or an hour.
- Korglikon – this drug is close in properties to Strofantin, also intended for intravenous administration. However, Korglikon is capable of a slightly longer duration than Strofantin.
The list of cardiac glycosides can be continued with drugs such as infusion of adonis, Adoniside, ankylosing spondylitis, tincture of lily of the valley, etc. However, they are rarely used to treat conditions associated with chronic heart failure. These drugs are used as sedatives for cardiac neurosis, neurasthenia, autonomic and vascular dystonia, or other conditions with a mild degree of circulatory disturbance. Before using them, consultation with a doctor is also necessary.
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