What are the adverse reactions that people may experience when taking antiarrhythmic medications?

When taken exactly as prescribed, medications can do wonders. They can help prevent heart attack and stroke. They can also prevent complications and slow the progression of coronary heart disease.

Some of the major types of commonly prescribed cardiovascular medications used to treat arrhythmias are summarized in this section. It's important to discuss all of the drugs you take with your doctor and understand their desired effects and possible side effects. Never stop taking a medication and never change your dose or frequency without first consulting your doctor.

Antiarrhythmic drugs

Symptomatic tachycardias and premature beats may be treated with a variety of antiarrhythmic drugs. These may be given intravenously in an emergency situation or orally for long-term treatment. These drugs either suppress the abnormal firing of pacemaker tissue or depress the transmission of impulses in tissues that either conduct too rapidly or participate in reentry.

In patients with atrial fibrillation, a *blood thinner (anticoagulant or antiplatelet) is usually added to reduce the risk of blood clots and stroke. Learn more about AFib medications.

When tachycardias or premature beats occur often, the effectiveness of antiarrhythmic drug therapy may be gauged by electrocardiographic monitoring in a hospital, by using a 24-hour Holter monitor or by serial drug evaluation with electrophysiologic testing.

The relative simplicity of antiarrhythmic drug therapy must be balanced against two disadvantages. One is that the drugs must be taken daily and indefinitely. The other is the risk of side effects. While side effects are a risk of all medication, those associated with antiarrhythmic drugs can be very hard to manage. They include proarrhythmia, the more-frequent occurrence of preexisting arrhythmias or the appearance of new arrhythmias as bad as or worse than those being treated.

Calcium channel blockers

Calcium channel blockers, also known as "calcium antagonists," work by interrupting the movement of calcium into heart and blood vessel tissue. Besides being used to treat high blood pressure, they're also used to treat angina (chest pain) and/or some arrhythmias.

Beta-blockers

Beta-blockers decrease the heart rate and cardiac output, which lowers blood pressure by blocking the effects of adrenalin. They're also used with therapy for cardiac arrhythmias and in treating angina pectoris.

Anticoagulants

Anticoagulants (blood thinners) work by making it harder for the blood to clot, or coagulate. They aren't designed to dissolve existing blood clots. They prevent new clots from forming or existing clots from getting larger. Because a common type of stroke is caused by a blood clot obstructing blood flow to the brain, anticoagulants are often prescribed for people with certain conditions to prevent the occurrence of a first stroke or to prevent the recurrence if the patient has already had a stroke. Anticoagulants are also given to certain people at risk for forming blood clots, such as those with artificial heart valves or who have atrial fibrillation.

Taking medications

• Take all medications exactly as prescribed.
• Never stop taking any prescription medication without first consulting your healthcare provider.
• If you have any side effects, tell your healthcare provider about them.
• Tell your healthcare provider about all your other drugs and supplements, including over-the-counter medications and vitamins (and holistic type supplements).
• Many rhythm disorders, especially tachycardias, respond to medications. Several drugs are now available and more are being developed. These drugs can't cure the arrhythmia, but they can improve symptoms. They do this by preventing the episodes from starting, decreasing the heart rate during the episode or shortening how long the episode lasts.
• Sometimes it's hard to find the best medication for a child. Several drugs may need to be tried before the right one is found. Some children must take medication every day; others need medications only when they have a tachycardia type episode. It's very important to take the medication as prescribed.
• All medications have side effects, including drugs to treat arrhythmias. Most of the side effects aren't serious and disappear when the dose is changed or the medication is stopped. But some side effects are very serious. That's why some children are admitted to the hospital to begin the medication. If your child is prescribed medication, it's very important that your child take the medication just the way the doctor prescribes it.
• It's often necessary to monitor how much of a drug is in your child's blood. The goal is to make sure there's enough of the drug to be effective, but not so much that harmful side effects occur. These blood tests require taking a small amount of blood from a vein or the finger. It's a good idea to talk to your child about this before the doctor visit.

Written by American Heart Association editorial staff and reviewed by science and medicine advisers. See our editorial policies and staff.

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