ANTI-ARRHYTHMIC DRUGS are a class of medications that are used to stop irregular heartbeat.
Arrhythmia is an irregular or abnormal heartbeat.
A heartbeat that is abnormally rapid or slow is called to as an arrhythmia or dysrhythmia.
Normal range of heartbeat is 60-100 beat per minute.
It occurs –
When the heart's electromagnetic impulses aren't functioning properly
Also occurs due to other Cardiac disease.
Types-
i. Bradycardia - abnormally too slow heart rate of below than 60 beats per minute are called bradycardia.
ii. Tachycardia - Adults with an abnormally high heart rate, more than 100 beats per minute are called tachycardia.
SYMPTOMS –
discomfort in the chest
a rapid heartbeat
Anxiety
a slow heartbeat
Respiration difficulty
CLASSIFICATION OF ANTI-ARRHYTHMIC DRUG
The anti-arrhythmic drugs you've listed are used to treat and prevent various types of cardiac arrhythmias (irregular heartbeats).
These drugs work in different ways to correct abnormal heart rhythms.
They are commonly classified based on the Vaughan Williams classification, which categorizes them into four main classes based on their mechanism of action.
This classification system is a widely used method to categorize anti-arrhythmic drugs, though it's important to note that some drugs have properties of more than one class, and this classification does not cover all anti-arrhythmic agents.
Here's a breakdown of the drugs you've listed according to the Vaughan Williams classification:
1. Class I: Sodium Channel Blockers
These drugs work by inhibiting the sodium channels in the cardiac cells, which reduces the ability of the heart cells to conduct electrical impulses.
Subdivided into:
A. Class IA:
Quinidine Sulphate, Procainamide Hydrochloride, Disopyramide Phosphate
They slow the conduction velocity, prolong the refractory period, and can prolong the QT interval.
B. Class IB:
Lidocaine Hydrochloride, Mexiletine Hydrochloride, Tocainide Hydrochloride
They have a minimal effect on conduction velocity and the refractory period in normal tissue but have more pronounced effects in ischemic or depolarized cells (e.g., during a heart attack).
C. Class IC:
Lorcainide Hydrochloride
They significantly slow conduction velocity but have a minimal effect on the refractory period. These are used for severe ventricular arrhythmias but can be proarrhythmic, especially in patients with structural heart disease.
2. Class II: Beta Blockers
This class is not represented in your list. Beta blockers work by blocking the beta-adrenergic receptors, leading to a decrease in heart rate and contractility.
3. Class III: Potassium Channel Blockers
These drugs prolong the refractory period by inhibiting potassium channels, which delays repolarization.
Amiodarone, Sotalol
4. Class IV: Calcium Channel Blockers
They work by blocking calcium channels in the heart and blood vessels, reducing heart rate and dilating blood vessels.
5. Other/Unclassified
Phenytoin Sodium
Primarily an anticonvulsant, but it can be used in the treatment of digoxin-induced arrhythmias and other specific conditions. Its mode of action in arrhythmias is similar to Class IB but it is not commonly classified under the standard Vaughan Williams categories.
Class | Mechanism of Action | Examples | Key Characteristics |
I: Sodium Channel Blockers | Inhibit sodium channels in cardiac cells | ||
IA | Slow conduction velocity, prolong refractory period, prolong QT interval | Quinidine Sulphate, Procainamide Hydrochloride, Disopyramide Phosphate | |
IB | Minimal effect on conduction velocity and refractory period in normal tissue, more pronounced in ischemic or depolarized cells | Lidocaine Hydrochloride, Mexiletine Hydrochloride, Tocainide Hydrochloride | |
IC | Significantly slow conduction velocity, minimal effect on refractory period | Lorcainide Hydrochloride | Used for severe ventricular arrhythmias, can be proarrhythmic in structural heart disease |
II: Beta Blockers | Block beta-adrenergic receptors, decrease heart rate and contractility | Not represented in your list | |
III: Potassium Channel Blockers | Prolong refractory period by inhibiting potassium channels, delay repolarization | Amiodarone, Sotalol | Amiodarone has characteristics of classes I, II, and IV; Sotalol has beta-blocking properties |
IV: Calcium Channel Blockers | Block calcium channels in heart and blood vessels, reduce heart rate, dilate blood vessels | Phenytoin Sodium | Primarily anticonvulsant, used for digoxin-induced arrhythmias and other conditions; similar to Class IB but not commonly classified in Vaughan Williams categories |