Identify a common side effect of beta-blockers.

Bradycardia is a recognized and common side effect of beta-blockers. These medications work by blocking the action of catecholamines (like adrenaline) on beta-adrenergic receptors in the heart and other tissues. This blockade leads to a decrease in heart rate and force of contraction, which can result in bradycardia. This effect can be beneficial in conditions such as hypertension and certain types of arrhythmias where a lower heart rate is desired.

In contrast, hypertension is not a side effect of beta-blockers; rather, these drugs are typically used to lower blood pressure. Weight gain, while reported by some patients, is less common and not universally recognized as a significant side effect compared to bradycardia. Increased heart rate would also not occur with beta-blockers, as their primary function is to reduce heart rate. Thus, recognizing bradycardia as a side effect is crucial for safe management when prescribing these medications.