Which medication is used for both arrhythmias and to slow heart rhythms?

The correct answer is Digoxin. Digoxin is a medication derived from the foxglove plant and is commonly used to treat heart conditions, particularly atrial fibrillation and heart failure. It works by increasing the force of myocardial contraction, which can improve heart efficiency in heart failure patients. Additionally, it slows down the heart rate by increasing vagal tone and decreasing conduction through the atrioventricular (AV) node, making it effective for managing arrhythmias where a slower heart rate is beneficial.

While other medications like adenosine, calcium-channel blockers, and beta-blockers do have effects on heart rhythm and rate, they serve different primary functions or indications. Adenosine is primarily used to terminate certain types of supraventricular tachycardias; calcium-channel blockers are used to treat hypertension and certain arrhythmias but do not necessarily slow heart rhythms in the same way as digoxin; and beta-blockers are effective in managing heart rate and preventing arrhythmias but do not directly increase myocardial contractility like digoxin does. Thus, digoxin uniquely fulfills the criterion of being effective for both arrhythmias and notably slowing the heart rate.