A patient Vipin 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 that inhibits the Na+/K+-ATPase pump in cardiac cells, leading to increased intracellular calcium and enhanced contractility. However, this inhibition also increases vagal tone, causing an exaggerated parasympathetic response to atropine.
**Why the Correct Answer is Right**
Atropine, an antimuscarinic agent, can block the muscarinic receptors stimulated by the increased vagal tone caused by digoxin. This blockade leads to a decrease in the parasympathetic effect on the heart, which can counteract the bradyarrhythmias and conduction disturbances associated with digoxin toxicity.
• The correct answer is related to the fact that digoxin increases vagal tone, which can be blocked by atropine.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not related to the interaction between digoxin and atropine.
**Option B:** This option is not accurate, as digoxin toxicity is not typically associated with increased sympathetic tone.
**Option C:** This option is incorrect, as digoxin toxicity is more likely to cause conduction disturbances and bradyarrhythmias, rather than tachycardia.
**Clinical Pearl / High-Yield Fact**
Atropine can be used to treat bradyarrhythmias associated with digoxin toxicity, but it should be used with caution, as it can also increase the risk of atrial fibrillation.
**Correct Answer: C. Tachycardia is not a common side effect of digoxin that can be blocked by atropine, but rather bradyarrhythmias and conduction disturbances, which are not listed as options. However, given the options, the closest answer is C.**