**Core Concept**
Tubercular pericarditis is a severe form of extrapulmonary tuberculosis that requires prompt and effective antitubercular treatment. The Revised National Tuberculosis Control Programme (RNTCP) recommends a specific category of anti-tubercular regimen for the treatment of this condition.

**Why the Correct Answer is Right**
The correct regimen for tubercular pericarditis is Category IV, which consists of a combination of four first-line anti-tubercular drugs: isoniazid, rifampicin, pyrazinamide, and ethambutol. This regimen is administered for a period of 2 months, followed by isoniazid and rifampicin for a further 4 months. The high dose of isoniazid and rifampicin in Category IV regimen helps to rapidly suppress the growth of Mycobacterium tuberculosis, thereby preventing further inflammation and cardiac damage.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as Category I is the standard regimen for new sputum smear-positive pulmonary tuberculosis patients.
**Option B:** This option is incorrect as Category II is the standard regimen for new sputum smear-negative pulmonary tuberculosis patients, including those with pleural effusion or miliary tuberculosis.
**Option C:** This option is incorrect as Category III is the standard regimen for patients with severe forms of tuberculosis, such as those with HIV co-infection or severe extrapulmonary tuberculosis, but it is not the recommended regimen for tubercular pericarditis.

**Clinical Pearl / High-Yield Fact**
It is essential to note that tubercular pericarditis is a medical emergency that requires prompt initiation of antitubercular therapy, along with supportive care to manage cardiac tamponade. The RNTCP guidelines emphasize the importance of early diagnosis and treatment to prevent mortality and morbidity.

**Correct Answer:** C. Category IV. Category IV regimen is the recommended treatment for tubercular pericarditis according to RNTCP guidelines.