|What Are Antiarrhythmics?
Antiarrhythmics are a group of medications to treat irregular heartbeats (arrhythmias). They either slow down or regulate a heart rate depending on the type of arrhythmia present. You may be injected with these drugs in an emergency situation or be told to take antiarrhythmic pills orally indefinitely. Currently there are no medications that can effectively speed up a slow heart rate. If the heart rate is persistently slow it will require a pacemaker or if it is so slow that there is a risk it will stop beating altogether (sudden cardiac arrest), an implantable cardioverter defibrillator (ICD) is necessary. Patients who are prescribed antiarrhythmics may also be prescribed other heart medications at the same time. These include calcium channel blockers (such as diltiazem and verapamil) and beta blockers (metoprolol and atenolol). Those diagnosed with atrial fibrillation (AF) may also be given anticoagulants or antiplatelet drugs to thin their blood (because AF increases the risk of blood clots and stroke).
How Do They Work?
Antiarrhythmics slow down a rapid heartbeat or they can regulate a premature or irregular heartbeat. Generally they work by blocking chemical reactions that facilitate electrical conduction in the heart (these reactions require calcium, potassium and sodium to take place). Antiarrhythmics interfere with calcium, potassium or sodium levels - in the process suppressing abnormal electrical impulses or slowing down the transmission of fast impulses as they travel through the heart. As a result, the heart beats more regularly and you experience fewer arrhythmia symptoms (fainting, dizziness and sweating).
What Are The Main Types Of Antiarrhythmics?
Different types of antiarrhythmics treat different conditions. Finding which one works for you can involve trial and error. Sometimes the medicine might make your arrhythmia worse (proarrhythmia) or it could cause more arrhythmia attacks. To begin with your doctor may monitor you closely with either a Holter monitor or electrophysiologic study (EPS). These studies will see how your heart reacts under different conditions while taking the medication.
There are 4 categories of antiarrhythmics:
Class I: Sodium-channel blockers. These medications help prevent tachyarrhythmia (abnormally fast heart beats), atrial fibrillation (irregular heartbeats), ventricular tachycardia (rapid rhythms in the lower chambers of the heart) and supraventricular tachycardia (episodic rapid heartbeats). They do this by regulating the flow of sodium in the heart. Medications in this group include flecainide, quinidine, tocainide, mexiletine, disopyramide and procainamide. The major advantage of flecainide is that it can be taken only when you need to (pill-in-the-pocket method, pop a pill when you feel a flutter coming on). This is in contrast to most other arrhythmia medications which must be taken daily.
Class II: Beta blockers. Taken by patients with high blood pressure or heart failure, beta blockers are also the mainstay treatment for arrhythmia. They are given to patients with fast heartbeats. Beta blockers slow the heart down and reduce its workload in the process (thereby helping to keep blood pressure low). They cause few major side effects which is why most patients prefer them. Popular brands include atenolol (Tenormin), metoprolol (Lopressor, Toprol XL), bisoprolol (Zebeta), bystolic (Nebivolol), nadolol, timolol (Blocadren) and carvedilol (Coreg).
Class III: This class of medicines slow the electrical impulses of the heart by blocking potassium. They are only likely to be prescribed if other, more common drugs, fail to work. Class III meds carry the risk of disturbing the heart's natural arrhythmia. For this reason most patients need to be hospitalized for the first few days of starting their medication to monitor their heart. Drugs in this category include sotalol, dofetilide and amiodarone. Those with an internal ICD are less likely to require shocks from their device while taking sotalol.
Class IV: These work like class II drugs but act by blocking calcium to the heart. Well known to patients with high blood pressure, verapamil and diltiazem are also common class IV antiarrhythmics. They are particularly good at controlling the heart rate of those with atrial flutter and atrial fibrillation. Class IV arrhythmia medications are generally well tolerated although they can reduce blood pressure and heart rate more than needed.
Digoxin (digitalis): Not included in the above categories, this medicine can be used as an antiarrhythmic. It can slow down fast heart rates.
What Are The Side Effects?
Possible side effects include the following:
Dizziness (due to low blood pressure)
Heart palpitations or irregular heartbeats.
Lung and breathing difficulties
If you notice any of side effects, report them to your doctor immediately.
Dangers Of Drug Interactions
As with all medications, let your doctor know what other medicines you are taking, including over the counter herbal remedies and vitamins. Some antiarrhythmics can have harmful effects when taken with other medicines. They can also decrease (or increase) the effectiveness of other drugs. For example beta blockers and sotalol can affect how your body reacts to insulin and oral diabetes medications. Or, amiodarone can make your skin more sensitive to the sun, so you will burn more easily.
When To Think Twice
Discuss the below with your doctor before agreeing to take antiarrhythmics.
Allergic to foods or dyes? Antiarrhythmics can make reactions worse.
Thinking of becoming pregnant, are you pregnant or breastfeeding?
Older than 60? Older patients are more prone to thyroid problems if they take antiarrhythmics.
About to have an operation or dental surgery?
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