Cardiac glycosides are cardiac and antiarrhythmic drugs of plant origin. Despite the natural composition, they should be used with extreme caution. According to statistics, glycoside intoxication occurs in 25% of patients who used drugs containing digoxin as the active substance. Such a high percentage is due to the peculiarities of the chemical structure and the pharmacological action of drugs. The article will describe the symptoms, diagnosis and prevention of glycoside intoxication. Correction of heart rhythms and other abnormalities will also be considered.
Glycosides
Organic compounds consisting of a carbohydrate residue and aglycone are glycosides (heterosides). Basically, these are crystalline or condensed substances with good solubility in alcohol and water.
Substances are widely distributed in nature, mainly inplant world. They are also obtained synthetically. Many heterosides are toxic, causing an increase or decrease in some body functions. In glycoside molecules, the furanoside and pyranoside residues are linked to the pharmacologically active part of the substance by aglycone through the O, N, S, and C atoms.
- O-glycosides are sugar derivatives in which the hydrogen atom is replaced by carbocyclic compound radicals that do not contain aromatic bonds or heterocyclic compounds. According to the nature of the pharmacological substance, the substances are divided into cerebrosides, cardiac glycosides, nitrogen-containing, glycoalkoloids.
- N-glycosides are derivatives of primary glycosylamine.
- S-glycosides are thioglycosides, derivatives of I-thiosaccharins. In nature, they are found in large quantities in black mustard.
- С-glycosides – demethylated glucose oxide. It has a powerful immunomodulatory effect. Unlike other groups, C-glycosides are incapable of hydrolysis.
Classification of medicinal glycosides
Systematize these substances according to the chemical structure of aglycones.
- Cyanogenic - glycosides of certain cyanogenic alcohols and ketones that release hydrocyanic acid during hydrolysis. Found in apricots, peaches, almonds.
- Saponins are nitrogen-free organic compounds with surface-active properties. They are used as expectorants, tonics, sedatives.
- Anthraglycosides are natural compounds that have as aglyconeanthracene derivatives.
- Cardiac glycosides are drugs with cardiotonic and antiarrhythmic properties. In large doses, substances become poisons and contribute to glycoside 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 buttercup, kutra, legume, lily family, as well as in the skin poison of some species of toads.
The most widely used preparations are foxglove ("Digitoxin", "Digoxin", "Celanin"), strophanthus ("Karglikon"), adonis ("Adonizide"). Cardiac glycosides have a selective effect on the myocardium, cause an increase in heart contractions, and reduce the heart rate.
Positive inotropic effect due to an increase in the calcium content in cardiomyocytes. This leads to suppression of sodium-calcium metabolism, in which one calcium ion is excreted from the cardiomyocyte in exchange for three sodium ions. As a result, the calcium content in the cytosol of the bulk of the myocardium increases, and the efficiency of contractions increases.
When therapeutic doses are observed, these effects appear. 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 typeaglycone.
Poisoning
As a rule, 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 glycoside intoxication may be due to an overdose or an abnormal response of the body to therapeutic doses due to various pathologies.
The body accumulates a large amount of sodium and calcium. In small doses, cardiac glycosides practically do not change the value of the resting potential, and at increased doses, they significantly reduce it. In case of 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 toxic effects can be cardiac and non-cardiac. 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.
- Decrease in heart rate (less than 60 beats per minute).
- Sinus arrhythmia.
- Complication of heart failure.
- Myocardial conduction failures.
- Stop the sinus node.
- Dizziness accompanied by pain.
- Color vision disorder.
- Insomnia.
- Delirious syndrome (delirium tremens, fever).
- Anorexia.
- Nausea.
- Spastic pain in the abdomen.
- Stool disorder.
Rare complications include:
- Gynecomastia is a pathological enlargement of the mammary gland with an increase in the volume of adipose tissue.
- Allergic reactions manifested on the skin.
- Immune thrombocytopenia.
Why the medicine starts acting like a poison
The main cause of glycoside intoxication is a change in pharmacokinetics in certain 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 action of cardiac glycosides.
- Hypothyroidism.
- Cardiomyopathy.
- Oxygen starvation of the myocardium.
- Hypokalemia.
- Hypercalcemia.
- An acid-base disorder characterized by an increase in cations (alkalosis).
- Hypomagnesemia.
- Hemodialysis.
- Past 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, it is necessary to provide assistance to the victim on their own. For thisrequired:
- Stop using cardiac glycosides.
- Ensure the complete rest of the victim.
- To slow down the absorption and circulation of toxic substances, take vaseline oil orally.
- To reduce the toxic effect, drink absorbent preparations (activated charcoal, "Smecta"). They will absorb the remaining glycosides. If the victim is unable to swallow the medicine on his own, it is administered through a tube.
Gastric lavage in case of glycoside intoxication by artificially induced vomiting is highly discouraged, as parasympathetic tone may increase, leading to a worsening of the condition.
Further resuscitation actions are performed by medical staff:
- Glucose and vitamin B6 are injected into a vein.
- If necessary, apply the method of artificial inhalation of the lungs.
- Anti-arrhythmia drugs are used to normalize the heart rhythm.
- In severe conditions, pacing and defibrillation are used.
Using an antidote
Fab-fragments of antibodies to digoxin ("Antidigoxin") are used as an antidote. As a rule, after its intravenous administration, the heart rhythm 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 content of digoxin in the body is slightly increased, 1-2 bottles of antidote are administered, and in severe cases - 5-6vials. If necessary, increase the dosage.
Possible Complications
Untimely recognition of glycoside intoxication can aggravate existing heart defects (heart failure, ventricular fibrillation). During failures of heart contractions, the brain is not sufficiently enriched with oxygen supplied with blood through the cerebral vessels. Lack of nutrients provokes the development of severe pathologies of the central nervous system (brain infarction, paralysis, parkinsonism).
Treatment of glycoside intoxication
The main diagnostic method in detecting complications of poisoning 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 ECG-diagnosed signs of glycoside intoxication will be sinus bradycardia, ventricular and supraventricular arrhythmias, and atrioventricular dissociation.
Therapy is prescribed taking into account the pathologies identified during the examination. Treatment only in a hospital. Doctors perform the following manipulations:
- To reduce the toxic effect, "Unithiol" 5%, 5 ml, 4 times a day, is administered intramuscularly. Disodium s alt, diluted in a 5% glucose solution, is also used to reduce the toxic effect, it is administered drip 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%, 1 ml.
- For dehydration, administer orallysolutions of sodium chloride and glucose 5%.
- Excitation suppressed by barbiturates.
- Cardiogenic collapse is treated with potassium chloride.
How to prevent poisoning
The main measure for the prevention of glycoside intoxication is the correction of the dosage of drugs. It must be carried out, taking into account other pathologies of the patient, as well as his age. Preventive measures:
- The use of cardiac glycosides is carried out according to the prescription of a cardiologist and under his strict control.
- If other pathologies are detected during therapy, medication is adjusted taking into account other prescribed drugs.
- Exclusion of products with an excess content of glycosides (apricots, peaches, beans).
- When using cardiac glycosides, regularly examine the content of sodium, calcium, and potassium in the blood. If necessary, correct the content of these elements in the body.
- Elderly patients should use heterosides very carefully, more often to be examined.
At the first manifestations of intoxication, stop taking drugs and call a doctor.
