Antiarrhythmic Medications

Antiarrhythmic medications are used to correct electrical disturbances of the heart. Sometimes, the heart can have difficulty with beating too fast, beating too slowly, or beating with an irregular heartbeat. Many rhythm disturbances of the heart are not serious, but for those that are, medication is given to keep the arrhythmia under control or to resolve it altogether.

There are many types of antiarrhythmic medications doctors use to manage electrical difficulties of the heart. There are medications to control atrial arrhythmias, in which the sinus node is not functioning properly. There are also medications to control rapid heartrate and medications to control ventricular arrhythmias.

How Do Antiarrhythmic Medications Work?

Antiarrhythmic medications work in a number of ways. Sometimes they are used to control the abnormal electrical impulses in the heart so that the normal electrical centers of the heart can take over and can conduct electricity normally through the heart.

There are basically four different types of antiarrhythmic medications. These include the following:

  • Class I Antiarrhythmic medications. These are mainly medications that act on the sodium channels of the heart cells. They slow the degree of electrical activity within the heart muscle. Class I antiarrhythmic medications include Tambocor, Norpace, Mexitil, Dilantin, Rhythmol, and Quinidex.
  • Class II Antiarrhythmic medications. These are also known as beta blockers. They block abnormal impulses in the heart that cause the heart to beat too rapidly. They react with things like epinephrine to reduce both the heart rate and the blood pressure. Class II antiarrhythmic medications include Sectrol, Tenormin, Kerlone, Zebeta, Ziac, Coreg, Cartrol, Normodyne, Trandate, Corgard, Levatol, Inderal, Biocadren, and Lopressor (metoprolol).
  • Class III Antiarrhythmic Medications. These consist of medications that act on the potassium channels in the heart, blocking the flow of potassium. This has the effect of slowing the electrical impulses within the heart muscle. Class III antiarrhythmic medications include amiodarone, Pacerone, Cordarone, Tikosyn, Betapace, Corvert, and Multaq.
  • Class IV Antiarrhythmic Medications. These act on the calcium channels of the heart muscle. Like class II agents, they reduce the pulse rate and blood pressure in the body. Class IV antiarrhythmic medications include diltiazem (Cardizem) and verapamil (sold as Isoptin, Verelan, Covera, and Calan).

Can Everyone Use Antiarrhythmic Medications?

Not everyone can take antiarrhythmic medications. They are generally used in emergency medical situations and cannot be used by people with the following conditions:

  • People who have a known allergic or hypersensitivity reaction to a specific medication.
  • Women who are pregnant.
  • Women who are breastfeeding.
  • People with a second or third degree heart block.
  • People with hypotension.
  • People with significant congestive heart failure.
  • People with aortic stenosis.
  • People in cardiogenic shock.
  • People with myasthenia gravis (applies only to the use of procainamide and quinidine).

What Are the Recommended Dosages of Antiarrhythmic Medications?

The actual recommended dose of antiarrhythmic medication depends on the particular drug being used and on other factors such as reactivity to the drug and age. Different people respond differently to antiarrhythmic agents so that a doctor’s care and pharmacist’s advice are necessary for the proper dosing of the medication.

Be sure to take the medications exactly as prescribed. It is dangerous to take extra doses of the medication no matter what symptoms you may be experiencing. In the same way, it is dangerous to stop taking the antiarrhythmic medication without asking for advice from your prescribing physician. A sudden stop of a medication for arrhythmia could lead to dangerous heart problems.

Antiarrhythmic medications are more effective when the blood levels remain constant in the bloodstream. In order to achieve this effect, you should evenly space the taking of the medication throughout the day, taking care not to miss any of the prescribed doses. Your doctor or pharmacist may be able to give you advice about how to take the medications if these medications are necessary to be taken during sleeping hours.

What Are the Side Effects of Taking Antiarrhythmic Medications?

There are adverse reactions that are common to taking most types of antiarrhythmic medications, including weakness, low blood pressure, light-headedness, fatigue, and slow heart rate.

Certain antiarrhythmic medications have unique side effects particularly. Every antiarrhythmic medication has the potential to result in new arrhythmias or the worsening of arrhythmias that already exist. This is a phenomenon doctors refer to as a “proarrhythmic effect”. Such an effect can result in an increase in the number of premature ventricular contractions or PVCs in the heart, the onset of ventricular tachycardia, ventricular fibrillation.

More serious effects can lead to the death of the individual. This effect can occur commonly when a person is given or takes excessive doses of the medication, if the medication is given intravenously, or when the arrhythmia being treated is already life-threatening.

More Precautions of Using Antiarrhythmic Medications

It is important to take these types of medications with caution if you have preexisting liver or kidney disease. If these conditions exist, a lower dosage of the medication may be required. Everyone taking an antiarrhythmic medication should have regular monitoring of their liver and kidney function.

  • ŸThose taking procainamide or quinidine need to be watched carefully in the presence of congestive heart failure.
  • ŸDisopyramide is an antiarrhythmic medication that should be taken with caution in those who have myasthenia gravis, congestive heart failure, glaucoma, or prostate enlargement.
  • ŸThose taking bretylium should be monitored for digoxin toxicity because the taking of the two medications together can contribute to worsening of ventricular arrhythmias or to congestive heart failure.

Anyone taking an antiarrhythmic drug should be monitored for electrolyte disturbances, such as hyperkalemia, hypokalemia, or hypomagnesemia, as these can change the effectiveness of the drugs. Any imbalances of electrolytes should be checked and managed promptly in order to avoid negative side effects. 

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