**Core Concept**
Digitalis poisoning, also known as digoxin toxicity, occurs when the levels of digoxin, a cardiac glycoside, exceed the therapeutic range. This can lead to various symptoms, including nausea, vomiting, visual disturbances, and cardiac arrhythmias.

**Why the Correct Answer is Right**
The primary treatment for digitalis poisoning involves administering medications that help counteract the effects of digoxin on the heart. **Digoxin-specific antibody fragments (Fab fragments)** are the preferred treatment, as they bind to digoxin and help remove it from the body. Other treatments, such as atropine for bradycardia and isoproterenol for heart block, may also be indicated in certain cases.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because atropine is actually indicated in digitalis poisoning for the treatment of bradycardia (slow heart rate).
**Option B:** This option is incorrect because isoproterenol is indicated in digitalis poisoning for the treatment of heart block (abnormal heart rhythm).
**Option C:** This option is incorrect because phenytoin is an antiepileptic medication and is not indicated in the treatment of digitalis poisoning.

**Clinical Pearl / High-Yield Fact**
In cases of digitalis poisoning, it is essential to remember that the treatment should focus on removing the digoxin from the body and managing any cardiac arrhythmias. The use of digoxin-specific antibody fragments (Fab fragments) is a key part of this treatment.

**Correct Answer: C. Pheynytoin is not indicated in digitalis poisoning.**