Drug of Choice for Digoxin induced Ventricular Tachycardia
The correct answer is likely lidocaine or another antiarrhythmic, but wait, I remember that digoxin toxicity is specifically managed with digoxin immune Fab. Wait, no—digoxin immune Fab is the antidote, but for arrhythmias, especially life-threatening ones like ventricular tachycardia, the treatment might involve other drugs. Let me think.
Digoxin toxicity can cause arrhythmias by increasing automaticity and decreasing the refractory period in cardiac tissue. The antidote, digoxin immune Fab, works by binding to digoxin, preventing it from interacting with the Na+/K+ ATPase pump. But for acute arrhythmias, especially ventricular tachycardia, the drug of choice is usually a potassium channel blocker like amiodarone. Alternatively, phenytoin is sometimes used because it can reduce the automaticity of the Purkinje fibers.
Wait, I need to verify. Some sources say phenytoin is preferred over lidocaine in digoxin toxicity because lidocaine can be less effective or even worsen the situation. Amiodarone is also an option. But the antidote itself (digoxin immune Fab) is used for severe toxicity, not just the arrhythmia. So for the arrhythmia, phenytoin or amiodarone might be the correct answer here.
Looking at the options provided, if the correct answer is phenytoin, then the explanation would focus on how phenytoin reduces intracellular sodium and calcium, which can help in digoxin-induced arrhythmias. Alternatively, if it's amiodarone, then that's the case. Another point is that lidocaine is not recommended in digoxin toxicity because it can lower the seizure threshold and might not be effective.
So, the core concept is the management of arrhythmias caused by digoxin toxicity. The correct drug of choice is phenytoin. The options are probably A. Lidocaine, B. Digoxin immune Fab, C. Phenytoin, D. Amiodarone. The correct answer would be C. Phenytoin. The explanation would need to detail why phenytoin is preferred over other options like lidocaine or amiodarone in this specific scenario.
**Core Concept**
Digoxin toxicity causes arrhythmias via Na+/K+ ATPase inhibition, increasing intracellular calcium and sodium. Phenytoin is the drug of choice for digoxin-induced ventricular tachycardia due to its ability to stabilize Purkinje fibers by blocking voltage-gated sodium channels.
**Why the Correct Answer is Right**
Phenytoin reduces intracellular sodium and calcium overload in cardiac myocytes, counteracting digoxin’s effects. It does not bind to digoxin but mitigates its arrhythmogenic potential by decreasing automaticity and conduction velocity in Purkinje fibers. This is critical in ventricular tachycardia