What is a common side effect experienced by patients taking beta-blockers?

Beta-blockers are a class of medications commonly prescribed for various cardiovascular conditions, such as hypertension, heart failure, and arrhythmias. One of the primary mechanisms of beta-blockers is their ability to lower heart rate by blocking the effects of adrenaline on beta-adrenergic receptors. This action leads to a common side effect known as bradycardia, which is characterized by a slower than normal heart rate.

Bradycardia can occur because beta-blockers reduce the heart's workload and slow down the electrical conduction through the heart. While this effect can be therapeutic for conditions where a high heart rate is detrimental, it can also lead to symptomatic bradycardia in some patients, manifesting as fatigue, dizziness, or fainting.

In contrast, the other options provided do not align with the pharmacological effects of beta-blockers. Hypertension and tachycardia are conditions that beta-blockers aim to treat, so they would not be considered common side effects. Nausea, while it can occur due to various medications, is not a hallmark side effect associated with beta-blockers specifically. Thus, bradycardia stands out as the expected outcome of beta-blocker therapy.