Some Side Effects
An abnormally slow heart rate (bradycardia)
Possible masking of low blood sugar levels
Impaired circulation in the trunk, arms, and legs
Raynaud syndrome Raynaud Syndrome Raynaud syndrome, a functional peripheral arterial disease, is a condition in which small arteries (arterioles), usually in the fingers or toes, narrow (constrict) more tightly than normal in... read more
Shortness of breath
Spasm of the airways (bronchospasm)
With some beta-blockers, an increase in the triglyceride (a fat) level
In people with glaucoma, increased pressure in the eye
These drugs are used to treat ventricular premature beats Ventricular Premature Beats A ventricular premature beat is an extra heartbeat resulting from abnormal electrical activation originating in the ventricles (the lower chambers of the heart) before a normal heartbeat would... read more , ventricular tachycardia Ventricular Tachycardia Ventricular tachycardia is a heart rhythm that originates in the ventricles (lower chambers of the heart) and produces a heart rate of at least 120 beats per minute (the normal heart rate is... read more , ventricular fibrillation Ventricular Fibrillation Ventricular fibrillation is a potentially fatal, uncoordinated series of very rapid, ineffective contractions of the ventricles (lower chambers of the heart) caused by many chaotic electrical... read more , and paroxysmal supraventricular tachycardia Paroxysmal Supraventricular Tachycardia (SVT, PSVT) Paroxysmal supraventricular tachycardia is a regular, fast (160 to 220 beats per minute) heart rate that begins and ends suddenly and originates in heart tissue other than that in the ventricles... read more . They are also used to slow the ventricular rate (how fast the heart's lower chambers—the ventricles—beat) in people with atrial fibrillation Atrial Fibrillation and Atrial Flutter Atrial fibrillation and atrial flutter are very fast electrical discharge patterns that make the atria (upper chambers of the heart) contract very rapidly, with some of the electrical impulses... read more or atrial flutter Atrial Fibrillation and Atrial Flutter Atrial fibrillation and atrial flutter are very fast electrical discharge patterns that make the atria (upper chambers of the heart) contract very rapidly, with some of the electrical impulses... read more .
People who have asthma should ask their doctor before taking these drugs.
Timolol is not available in the United States.
Calcium channel blockers
Low blood pressure
Only certain calcium channel blockers, such as diltiazem and verapamil, are useful. They are used to slow the ventricular rate in people who have atrial fibrillation or atrial flutter and to treat paroxysmal supraventricular tachycardia.
Diltiazem and verapamil slow the conduction of electrical impulses through the atrioventricular node.
Certain people with Wolff-Parkinson-White syndrome Wolff-Parkinson-White (WPW) Syndrome Wolff-Parkinson-White syndrome is a disorder in which an extra electrical connection between the atria and the ventricles is present at birth. People may have episodes of a very rapid heartbeat... read more should not take verapamil or diltiazem.
If the dose is too high, distortion of color vision, making objects appear greenish yellow
Digoxin slows conduction of electrical impulses through the atrioventricular node. Digoxin is used to decrease the ventricular rate in people who have atrial fibrillation or atrial flutter and to treat paroxysmal supraventricular tachycardia.
Potassium channel blockers
For all potassium channel blockers: Arrhythmias and low blood pressure
For amiodarone: scarring in the lungs (pulmonary fibrosis) and thyroid, liver, and eye abnormalities.
For sotalol (also a beta-blocker): the same side effects as beta-blockers
These drugs are used to treat ventricular premature beats, ventricular tachycardia, ventricular fibrillation, atrial fibrillation, and atrial flutter.
Because amiodarone can be toxic, it is used for long-term treatment only in some people who have serious or very bothersome arrhythmias.
Bretylium is used only for short-term treatment of life-threatening ventricular tachycardias.
Azimilide, bretylium, and vernakalant are not available in the United States.
Spasm of the airways
Flushing (for a short time)
Adenosine slows conduction of electrical impulses through the atrioventricular node.
Adenosine is used to end episodes of paroxysmal supraventricular tachycardia.
People who have asthma are not given this drug.
Sodium channel blockers
Arrhythmias (which can be fatal, particularly in people who have a heart disorder)
For some drugs:
Retention of urine
In people with glaucoma, increased pressure in the eyes
These drugs slow the conduction of electrical impulses through the heart.
These drugs are used to treat ventricular premature beats, ventricular tachycardia, and ventricular fibrillation and to convert atrial fibrillation or atrial flutter to normal rhythm (cardioversion).
Except for lidocaine and mexiletine, these drugs may also be used to prevent episodes of atrial fibrillation or atrial flutter and, less commonly, paroxysmal supraventricular tachycardia.