Cardiac glycosides are herbal cardiological and antiarrhythmic drugs. Despite the natural composition, they should be used with extreme caution. According to statistics, glycosidic intoxication occurs in 25% of patients who use drugs containing digoxin as an active substance. Such a high percentage is due to the peculiarities of the chemical structure and pharmacological action of drugs. The article will describe the symptoms, diagnosis and prevention of glycoside intoxication. Correction of heart rhythms and other disorders will also be considered.
Glycosides
Organic compounds consisting of a carbohydrate residue and aglycon are glycosides (heterosides). Basically, these are crystalline or condensed substances with good solubility in alcohol and in water.
Substances are widely distributed in nature, mainly in the plant world. They are also obtained synthetically. Many heterosides are toxic, causing an increase or decrease in some functions of the body. In glycoside molecules, the furanoside and pyranoside residues are linked to the pharmacologically active part of the substance by an aglycon through O, N, S, and C.
- O-glycosides are derivatives of sugars in which the hydrogen atom is replaced by radicals of a carbocyclic compound that does not contain aromatic bonds or heterocyclic compounds. By the nature of the pharmacological substance, substances are divided into cerebrosides, cardiac glycosides, nitrogen-containing, glycoalkoloids.
- N-glycosides are derivatives of primary glycosylamine.
- S-glycosides - thioglycosides, derivatives of I-thiosaccharines. In nature, in large quantities are found in black mustard.
- C-glycosides - demethylated glucose oxide. It has a powerful immunomodulatory effect. Unlike other groups, C-glycosides are not capable of hydrolysis.
Classification of drug glycosides
Systematize these substances by the chemical structure of aglycones.
- Cyanogenic - glycosides of certain cyanogenic alcohols and ketones that produce hydrocyanic acid during hydrolysis. Contained in apricots, peaches, almonds.
- Saponins are nitrogen-free organic compounds with surface-active properties. They are used as expectorants, tonic, sedatives.
- Antraglycosides are natural compounds having anthracene derivatives as aglycone.
- Cardiac glycosides are drugs with cardiotonic and antiarrhythmic properties. In large doses, the substances become poisons and contribute to glycosidic intoxication. Symptoms of poisoning depend on the mechanism of action of the substance on the myocardium.
Cardiac Glycosides: General Description
Cardiotonic drugs are called cardiac glycosides. In nature, these substances are found in plants of the family buttercup, coutra, bean, and lily, as well as in the skin poison of some species of toads.
The most widely used drugs are digitalis (Digitoxin, Digoxin, Celanin), strophanthus (Karglikon), adonis (Adonizid). Cardiac glycosides have a selective effect on the myocardium, cause increased heart contractions, and reduce the heart rate.
The positive inotropic effect is due to an increase in the calcium content in cardiomyocytes. This leads to the suppression of sodium-calcium metabolism, in which one calcium ion from the cardiomyocyte is excreted in exchange for three sodium ions. As a result of this, the calcium content in the cytosol of the main mass of the myocardium increases, and the effectiveness of contractions increases.
When therapeutic doses are observed, these effects are manifested. Decreased conductivity (dromotropic effect) and increased excitability of the elements of the heart system, except for the sinus node (batmotropic effect). are signs of glycoside intoxication. Symptoms of poisoning depend on the concentration of the drug, on the type of aglycon.
Poisoning
Typically, this serious condition is caused by the toxic effects of cardiac glycosides. The course of the pathological condition is acute, the chronic form is practically not observed. The pathogenesis of glycosidic intoxication may be due to an overdose or an abnormal reaction of the body to therapeutic doses due to various pathologies.
A large amount of sodium and calcium accumulates in the body. In small doses, cardiac glycosides practically do not change the value of the resting potential, and with increased doses, they significantly reduce it. With poisoning, the automatism of the nodes, bundles and fibers of the heart increases, which contributes to the manifestation of ectopic activity.
Symptoms of glycoside intoxication
Manifestations of a toxic effect can be cardiac and extracardiac. The first are characterized by the effect of drugs on the myocardium. The second - neurological and gastrointestinal disorders. Symptoms of glycoside intoxication include:
- Non-paroxysmal tachycardia.
- Polytopic ventricular tachycardia.
- Heart rate reduction (less than 60 beats per minute).
- Sinus arrhythmia.
- Complications of heart failure.
- Failures of myocardial electrical conductivity.
- Sinus node stop.
- Dizziness accompanied by pain.
- Color vision disorder.
- Insomnia.
- Delirious syndrome (delirium tremens, fever).
- Anorexia.
- Nausea.
- Cramping pains in the abdomen.
- Upset stool.
Rare complications include:
- Gynecomastia is a pathological increase in the mammary gland with an increase in the volume of adipose tissue.
- Allergic reactions manifested on the skin.
- Immune thrombocytopenia.
Why does the medicine begin to act like poison
The main reason for glycoside intoxication is a change in pharmacokinetics in some pathological conditions. Sometimes there is a deliberate increase in the dose of drugs due to suicidal tendencies. The development of glycoside intoxication in the elderly contributes to increased sensitivity to cardiac drugs.
Risk factors contributing to poisoning:
- The use of drugs that enhance the pharmacological effect of cardiac glycosides.
- Hypothyroidism
- Cardiomyopathy
- Myocardial oxygen starvation.
- Hypokalemia.
- Hypercalcemia.
- An acid-base balance disorder characterized by an increase in cations (alkalosis).
- Hypomagnesemia.
- Hemodialysis.
- Postponed cardiac surgery.
First aid
As you know, the effectiveness of therapy often depends on the speed of action. In case of poisoning, it is necessary to immediately call an emergency medical team for resuscitation by doctors. Prior to their arrival, assistance should be provided to the injured person. This requires:
- Stop use of cardiac glycosides.
- Ensure complete peace of mind.
- To slow down the absorption and circulation of toxic substances, take vaseline oil inside.
- To reduce the toxic effect, drink absorbent preparations (activated carbon, Smecta). They will absorb glycoside residues. If the victim is not able to swallow the medicine on his own, he is administered through a probe.
Gastric lavage during glycosidic intoxication by artificially induced vomiting is highly not recommended, as parasympathetic tone may increase, which will lead to a worsening of the condition.
Further resuscitation is performed by medical staff:
- Glucose and vitamin B6 are injected into a vein.
- If necessary, apply the method of artificial lung inhalation.
- To normalize heart rhythm, anti-arrhythmia drugs are used.
- In severe conditions, pacing and defibrillation are used.
Use of antidote
Fab fragments of antibodies to digoxin (“Antidigoxin”) are used as antidote. As a rule, after its intravenous administration, the heart rate is restored within an hour. "Antidigoxin" binds not only digoxin, but also other glycosides. True, to neutralize them, it is necessary to increase the dose of the antidote.
If the total digoxin content in the body is slightly increased, 1-2 bottles of antidote are administered, and in severe cases, 5-6 bottles. If necessary, an increase in dosage is allowed.
Possible complications
Late recognition of glycoside intoxication can aggravate existing heart defects (heart failure, ventricular fibrillation). During heart failure, the brain is not sufficiently enriched with oxygen entering the blood through the cerebral vessels. Lack of nutrients provokes the development of severe CNS pathologies (cerebral infarction, paralysis, parkinsonism).
Glycoside intoxication treatment
The main diagnostic method for identifying poisoning complications is the electrophysiological method for studying the biopotentials of the heart. The drugs cause relaxation of the myocardium and change the direction of repolarization. The main signs of glycosidic intoxication diagnosed by ECG will be sinus bradycardia, ventricular and supraventricular arrhythmias, atrioventricular dissociation.
Therapy is prescribed taking into account the pathologies identified during the examination. Treatment is only in a hospital. Doctors perform such manipulations:
- To reduce the toxic effect, Unitiol 5% 5 ml 4 times a day is administered intramuscularly. Disodium salt, diluted in a 5% glucose solution, is also used to reduce the toxic effect, drip is administered for the first 3-4 hours.
- To reduce myocardial excitability and eliminate tachycardia, Anaprilin is prescribed 20 mg three times a day.
- The manifestation of bradycardia and nausea is stopped by the introduction of Atropine sulfate 0.1% in 1 ml.
- When dehydrated, solutions of sodium chloride and glucose 5% are transversely administered.
- Excitation is suppressed by barbiturates.
- Cardiogenic collapse is eliminated with potassium chloride.
How to prevent poisoning
The main preventive measure of glycoside intoxication is the dosage adjustment of drugs. It must be carried out, take into account other pathologies of the patient, as well as his age. Preventive actions:
- The use of cardiac glycosides is carried out as prescribed by the cardiologist and under his strict control.
- If other pathologies are detected during therapy, the medication is adjusted taking into account other prescribed drugs.
- Exclusion of foods with excessive glycosides (apricots, peaches, beans).
- When using cardiac glycosides, regularly check for blood sodium, calcium, potassium. If necessary, carry out the correction of the content of these elements in the body.
- Elderly patients should use heterosides very carefully, more often undergo examination.
At the first manifestations of intoxication, it is necessary to stop taking the drugs and call a doctor.