What is the most common side effect of using beta-blockers?

The most common side effect of using beta-blockers is bradycardia and fatigue. Beta-blockers work by blocking the effects of epinephrine on the beta-adrenergic receptors, which leads to a decrease in heart rate and myocardial contractility. This action effectively lowers blood pressure and can help with conditions such as hypertension and certain types of heart disease.

Bradycardia, characterized by a slower-than-normal heart rate, occurs because beta-blockers reduce the electrical conduction through the heart. Many patients may also experience fatigue as their bodies adapt to the medication, particularly if they've had an increase in exercise tolerance or if their heart's workload has been reduced significantly. This fatigue can result from both the reduced heart rate and the overall calming effect beta-blockers have on the body's sympathetic nervous system.

While other side effects, such as insomnia or dry mouth, can occur with beta-blocker use, bradycardia and fatigue are more common and directly related to the pharmacological effects of these medications, making them the most prevalent side effects experienced by patients.