**Core Concept**
Pericarditis is an inflammatory condition of the pericardium, the fibroserous sac surrounding the heart. Certain drugs can induce pericarditis as a side effect, often through mechanisms involving immune system activation or direct toxicity to the pericardial tissue.

**Why the Correct Answer is Right**
Procainamide, a Class IA antiarrhythmic drug, can cause pericarditis in some patients. This is thought to be due to its ability to induce a lupus-like reaction, characterized by the production of autoantibodies against the pericardium. Other drugs, such as hydralazine and methysergide, can also cause pericarditis through similar mechanisms. These drugs can trigger an immune response that leads to inflammation and damage to the pericardium.

**Why Each Wrong Option is Incorrect**
* **Option A:** Hydralazine can indeed cause pericarditis, but it is not the only correct answer. This option is incorrect because it does not acknowledge the other correct options.
* **Option B:** Bretylium is an antiarrhythmic drug that does not commonly cause pericarditis. This option is incorrect because it is not a known perpetrator of pericarditis.
* **Option C:** Amiodarone can cause a range of side effects, but pericarditis is not a common one. This option is incorrect because it is not a typical cause of pericarditis.
* **Option D:** Methysergide can cause pericarditis, making it a correct answer. This option is not incorrect, but rather a correct answer that was listed last.

**Clinical Pearl / High-Yield Fact**
When considering a patient with suspected pericarditis, it is essential to review their medication list for potential culprits. Certain drugs, such as procainamide, hydralazine, and methysergide, can induce pericarditis through immune system activation or direct toxicity.

**Correct Answer:** d. Methysergide.