A patient has been taking digoxin for several years and is about to receive atropine for some other indication. A common side effect of digoxin that can be blocked by atropine is:
**Core Concept**
Digoxin is a cardiac glycoside used to treat heart failure and atrial fibrillation. It increases the force of cardiac contractions by inhibiting the Na+/K+-ATPase pump, leading to increased intracellular calcium and enhanced contractility. However, digoxin can cause various side effects, including arrhythmias, due to its effect on the heart's electrical conduction system.
**Why the Correct Answer is Right**
Atropine can block the muscarinic receptor-mediated vagal effects on the heart, which can counteract the arrhythmogenic effects of digoxin. Digoxin can cause a vagally-mediated bradycardia, which can be exacerbated by the vagolytic effect of atropine. However, atropine can also block the vagal effects that contribute to digoxin-induced arrhythmias, such as atrioventricular (AV) block. By blocking the muscarinic receptors, atropine can increase the heart rate and improve cardiac output, thereby reducing the risk of digoxin-induced arrhythmias.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the interaction between digoxin and atropine.
**Option B:** This option is not a known side effect of digoxin that can be blocked by atropine.
**Option C:** This option is not a common side effect of digoxin that can be alleviated by atropine.
**Clinical Pearl / High-Yield Fact**
When administering atropine to patients taking digoxin, clinicians should be aware of the potential for increased heart rate and arrhythmias, and monitor the patient closely for signs of digitalis toxicity.
**Correct Answer:** C. Ventricular arrhythmias.