Drugs used to treat abnormal heart rates and rhythms (arrhythmias)
Other antiarrhythmic drugs
Abnormalities in heart rhythm and rate, known as arrhythmias, are caused by a disturbance in the electrical signals that control heart action. Often, minor disturbances do not need treatment. However, some arrhythmias do require treatment to restore normal heart rhythm, thereby reducing symptoms such as palpitations, shortness of breath, light-headedness, and chest pain.
Antiarrhythmics are commonly prescribed to treat the arrhythmias atrial fibrillation and supraventricular tachycardia, both of which cause the heart to beat very rapidly. They are also used to treat ventricular arrhythmia, which may develop after a heart attack (see Myocardial infarction) and, if left untreated, may lead to cardiac arrest.
Commonly used antiarrhythmics include beta-blockers, the calcium channel blocker drug verapamil, and the digitalis drug digoxin. There are various other types of antiarrhythmics, some of which are mostly used to treat ventricular arrhythmias.
How are they used?
Once an antiarrhythmic is required, you may have to take the drug indefinitely. For long-term treatment, the drugs are given orally, and initially you may need to take several doses a day. When your heartbeat has been stabilized, your doctor may test the drug levels in your blood in order to correct the dose.
The type of drug your doctor selects depends on which form of arrhythmia you have. For example, a beta-blocker, calcium channel blocker, or the digitalis drug digoxin may be useful in reducing a rapid heart rate in atrial fibrillation; flecainide or amiodarone may be used to restore a regular rhythm in atrial fibrillation; and mexiletine or lidocaine may be used to treat ventricular arrhythmia.
If you have developed arrhythmia suddenly and the condition is severe, you may be given a drug such as adenosine intravenously as an emergency measure to restore normal heart activity. When the initial symptoms have been brought under control, your doctor may prescribe drugs for long-term treatment to prevent future attacks.
What are the side effects?
Many types of these drugs reduce blood pressure. This may cause light-headedness when you stand up. You may also experience nausea and blurred vision.
Other side effects are specific to certain drugs. For example, amiodarone may cause skin sensitivity to sunlight and may also affect the function of the thyroid gland and lungs. If you are taking the digitalis drug digoxin, contact your doctor immediately if you experience nausea, diarrhoea, vomiting, or visual disturbances. These symptoms may indicate that the dose is too high.
You should tell your doctor if you are taking other drugs because of the risk of an adverse interaction with an antiarrhythmic. You should not stop taking an antiarrhythmic without consulting your doctor because abrupt withdrawal of the drug may make your condition worse.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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