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Antiarrhythmic drugs are drugs that normalize abnormal heart rhythm - tachycardia (tachycardia) or bradycardia (bradycardia). They affect the electrical activity of the heart. Used temporarily (in the form of a drip or administered orally), they may stop the fibrillation attack or, if used for a long time, reduce the risk of its recurrence.

Antiarrhythmic drugsdifficult to divide into specific groups, eg taking into account the chemical structure or mode of action. Why? Because in selecting the appropriate method of treating arrhythmia, attention is paid to many different factors, including comorbidities, general he alth of the patient and the presence of congenital or acquired heart defects.

Unfortunately, there are no universal treatment regimens that would guarantee the best efficacy and safety. Even with the same disease, there is no guarantee that each patient will react in the same way to the administered drug, let alone the same dose.

With many attempts to classify these drugs, the problem has always been a very complex mechanism of action of many of them, and therefore one preparation could be assigned to two different groups. Therefore, these classifications were sometimes not very precise.

Antiarrhythmic drugs - Vaughan Williams' division

Vaughan Williams undertook one of these divisions in the 1970s. To this day, it is the most widely used classification of antiarrhythmic drugs. In this classification, he took into account the basic mechanisms of action of these measures.

The Williams classification has undergone two significant modifications since its inception. In 1972 its creator included a new class IV, ie the class of calcium antagonists, which is now divided by some authors into two subclasses. Probably along with the development of medicine, this classification will change.

The current breakdown of Vaughan Williams is as follows:

  • class I blocks sodium channels by acting directly on cell membranes

IA - disopyramide, procainamide, quinidine, ajmaline, prajmaline

- application: ventricular arrhythmias, prevention of paroxysmal recurrent atrial fibrillation (caused by overactivity of the vagus nerve), drugs from this group can unfortunately cause uncontrolled and difficult to control cardiac arrhythmias, and evenventricular fibrillation

IB - lidocaine, phenytoin, mexiletine, tocainide, aprindine

-use: treatment of myocardial infarction and prevention of another one

IC - flecainide, enkainide, propafenone, lorkainide

- application: prevention of paroxysmal atrial fibrillation, treatment of recurrent tachyarrhythmias (i.e. accelerated heartbeat with simultaneous disturbance of its rhythm).

  • class II are sympatholytic drugs (a group of drugs that suppress the sympathetic nervous system) - most drugs in this class are beta-blockers

- propranolol, timolol, metoprolol, atenolol
- use - in permanent treatment they reduce mortality due to myocardial infarction, also prevent recurrent tachyarrhythmias, reduce exercise-related arrhythmias.

  • class III regulates the outflow of potassium from the cell - prolongs repolarization

- amiodarone, sotalol, bretylium, nibentan, ibutilide, dofetilide
- application - in Wolff-Parkinson-White syndrome, it is a congenital disorder of electrical impulse conduction in the heart, also e.g. sotalol - is used to treat ventricular tachycardia and atrial fibrillation.

  • class IV affects calcium channels

- verapamil, diltiazem
- use - preventing recurrences of paroxysmal supraventricular tachycardias, reducing the frequency of ventricular contractions in patients with atrial fibrillation.

The Vaughan Williams classification of antiarrhythmic drugs does not include two other drugs successfully used in modern medicine. They are:

  • adenosine, having a strong but short effect on the sinus and atrioventricular nodes in the heart
  • digoxin, a drug used in heart failure, increasing the tone of the parasympathetic system and affecting both of the above-mentioned nodes

Both drugs are used to treat supraventricular tachycardia.

Effects and effects of certain substances with antiarrhythmic properties

Propranolol

It is an organic chemical compound, belonging to the group of non-selective beta-blockers, and its action is based on blocking beta1 and beta2 receptors. The action of beta-blockers reduces the heart rate and the force of its contraction and blood pressure. They protect the heart against physical exertion or stress, and limit the influence of the sympathetic nervous system during rest.

Propranolol is used orally to treat:

  • hypertension
  • angina
  • in the prevention of heart attackheart in patients with coronary artery disease
  • to control supraventricular and ventricular arrhythmias
  • to reduce situational and generalized anxiety
  • propranolol is also used in the form of an intravenous injection solution in conditions requiring immediate treatment - cardiac arrhythmias or thyroid crisis, especially when they are life-threatening

Possible side effects:

  • nightmares, drowsiness, but also insomnia, fatigue and exhaustion
  • decrease in heart rate (bradycardia)
  • nausea, vomiting, diarrhea
  • dizziness, sensory disturbances - pins and needles and numbness
  • heart failure worsening
  • hypotension (including postural hypotension) and fainting associated with it

Diltiazem hydrochloride

A chemical that belongs to a group of drugs called calcium channel blockers (or calcium channel blockers) is a derivative of the benzothiazepine.

It has an effect on blood vessels - it reduces the tension of the smooth muscles of the vessel walls and their expansion, mainly in the arteries. The direct effect of this action is the reduction of blood pressure, which is especially important in people with hypertension. It should be noted that it does not lower blood pressure in people for whom it is normal.

Diltiazem is also used in the treatment of coronary arteries. Extended coronary arteries can transport more oxygen to the heart muscle. As a result, patients suffering from angina have a greater tolerance of exercise. The frequency of angina pains also decreases.

Diltiazem also has a direct effect on how the heart works, including its conductive system, which is responsible for the generation and conduction of the electrical impulses that regulate the heart's rhythm.

Diltiazem side effects

  • peripheral edema
  • headaches
  • dizziness
  • nervousness, insomnia
  • AV block, palpitations, decreased heart rate (bradycardia)
  • sudden but transient reddening of the face
  • orthostatic hypotension and related syncope
  • constipation, indigestion, stomach pain, nausea, vomiting, diarrhea
  • increased liver enzymes

Digoxin

Organic chemical compound from the group of glycosides, obtained from foxglove. It has a negative effect on theand dromotropic, which means that it reduces the heart rate and slows conduction in the atrioventricular node. This action is used in the treatment of some supraventricular arrhythmias, especially chronic atrial flutter and atrial fibrillation, as well as heart failure in children (it is the first-line drug).

However, the emergence of new drugs with proven efficacy in the treatment of heart failure (e.g. angiotensin II receptor antagonists, angiotensin converting enzyme inhibitors, beta-blockers, spironolactone) made digoxin less and less used in modern medicine.

Side effects

  • arrhythmias: atrioventricular block, extra ventricular contractions
  • nausea, vomiting, abdominal pain, anorexia
  • headaches and dizziness
  • fainting
  • insomnia
  • visual disturbance
  • mental disorders, depression and a general feeling of weakness

Amiodaron

An organic chemical compound, used as an antiarrhythmic drug and classified as class III according to Vaughan Williams' classification, although it also exhibits the properties of antiarrhythmic drugs from other groups, including some properties of group I drugs (e.g. stabilizes cell membranes). The mechanism of action of amiodarone is mainly related to the inhibition of potassium channels, i.e. reducing the flow of potassium ions from the cells.

Indication for use:

  • Wolff-Parkinson-White syndrome,
  • atrial fibrillation and flutter, paroxysmal supraventricular tachyarrhythmias
  • ventricular arrhythmias

Side effects:

  • microcomponents in the cornea, they form just below the pupil, they may be accompanied by seeing a colored halo around objects, especially when looking at them in bright light
  • nausea, vomiting, taste disturbance
  • photosensitivity, visual acuity disturbance
  • bradycardia
  • occurrence or worsening of arrhythmias

Metoprolol

An organic chemical compound, used as a beta-blocker drug, which reduces the heart rate and the force of its contraction, reduces the stroke volume and lowers blood pressure.

The preparation is indicated:

  • in the treatment of hypertension
  • to treat angina
  • in the treatment of cardiac arrhythmias,
  • helpful in patients with hyperthyroidism
  • it is also used immediately after a heart attack (starting as early as possibletreatment with metoprolol reduces the area of ​​necrosis and the risk of ventricular fibrillation).

Side effects:

  • fatigue, general weakness
  • hypotension (including orthostatic) and related headaches and dizziness
  • decrease in heart rate (bradycardia)
  • imbalance (combined with fainting)
  • palpitations, shortness of breath (especially after exercise)
  • nausea, diarrhea, constipation, abdominal pain

Antirrhythmic drugs - precautionary measures

There are a few important things to keep in mind when taking anti-arrhythmic medications.

First of all, these medications must be taken regularly, preferably at fixed times and as prescribed by your doctor.

Second - during therapy with, for example, verampil, you cannot drink alcohol. This drug inhibits the activity of alcohol dehydrogenase, which is an enzyme that breaks down ethyl alcohol. In this way, the concentration of alcohol in the blood increases.

Also, do not combine antiarrhythmic drugs with preparations containing caffeine and energy drinks, especially if the patient is also a coffee lover.

It is assumed, however, that drinking up to 300 mg of caffeine a day, or about three cups, should be safe for patients. Larger amounts may cause pressure spikes and cardiac arrhythmias.

Another thing to remember is that the heart that beats irregularly can be helped (but also harmed) with a diet.

To function properly, this organ requires: potassium, magnesium and calcium. People who take certain medications, e.g. diuretics, or follow restrictive diets, the so-called "fasts" may be deficient in these minerals.

That is why doctors very often recommend taking supplements with these elements. People who eat a lot of processed products also suffer from potassium, magnesium and calcium deficiencies, and this unfortunately hurts the heart - and not only it.

About the authorKarolina NowakA pharmaceutical technician by education. Currently, he is professionally fulfilled working in a pharmacy. Empathetic, sensitive and fond of contact with other people. Privately, a lover of a good book.

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