**Core Concept**
The question is testing the understanding of the concept of a narrow therapeutic window in antiarrhythmic drugs, which requires careful dosing to avoid toxicity while maintaining efficacy. The drug in question has a narrow therapeutic index, meaning small changes in plasma concentration can lead to either ineffective treatment or toxicity.

**Why the Correct Answer is Right**
The correct answer involves a dosing regimen that ensures the plasma concentration remains above the minimum therapeutic level, despite the narrow therapeutic window. This can be achieved by administering the drug at regular intervals, allowing the concentration to rise to a safe level above the minimum therapeutic level and then decreasing to a safe level below the toxic threshold before the next dose. This approach is known as **proportional dosing** or **loading-dosing**.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not account for the narrow therapeutic window of the drug. A fixed dose regimen would not ensure that the plasma concentration remains above the minimum therapeutic level, increasing the risk of toxicity.
* **Option B:** This option is incorrect because it does not provide a dosing schedule that would maintain the plasma concentration above the minimum therapeutic level. A single dose may not be sufficient to achieve this, and the duration of action may not be sufficient to prevent a lethal arrhythmia.
* **Option C:** This option is incorrect because it does not provide a dosing schedule that would maintain the plasma concentration above the minimum therapeutic level. The dosing interval may be too long, allowing the concentration to drop below the therapeutic level and increasing the risk of a lethal arrhythmia.

**Clinical Pearl / High-Yield Fact**
When dealing with drugs that have a narrow therapeutic window, it is essential to use a dosing regimen that ensures the plasma concentration remains above the minimum therapeutic level to prevent toxicity. This can be achieved through proportional dosing or loading-dosing, which involves administering multiple doses at regular intervals to maintain a safe and effective plasma concentration.

**Correct Answer:**
To be completed: You provided the answer but not the options.