Okay, let's tackle this question about which anti-tubercular drug may precipitate gout. First, I need to recall the drugs used in treating tuberculosis. The main ones are isoniazid, rifampin, pyrazinamide, ethambutol, and maybe others like streptomycin or levofloxacin. Now, gout is related to hyperuricemia, so the question is about a drug that increases uric acid levels.

Pyrazinamide comes to mind. I remember that it's known to cause hyperuricemia and can lead to gout attacks. The mechanism is that pyrazinamide is metabolized to pyrazinoic acid, which is excreted through the kidneys. This can compete with uric acid for excretion, leading to increased uric acid levels. Alternatively, it might interfere with urate transporters in the kidneys, reducing uric acid excretion.

Let me check the other options. Isoniazid might cause liver toxicity but not gout. Rifampin can cause enzyme inductions but not hyperuricemia. Ethambutol's side effects are optic neuritis and peripheral neuropathy, not gout. So the correct answer is pyrazinamide. The clinical pearl here is that pyrazinamide is a known cause of hyperuricemia, so patients on it should be monitored for gout, especially if they have risk factors. Also, patients with a history of gout should be cautious or given prophylactic treatment like allopurinol.

**Core Concept**
This question tests knowledge of anti-tubercular drugs and their adverse effects, specifically hyperuricemia-induced gout. Pyrazinamide is uniquely associated with this complication due to its metabolic pathway and renal urate excretion interference.

**Why the Correct Answer is Right**
Pyrazinamide is metabolized to pyrazinoic acid, which is excreted via the kidneys. This process competes with uric acid for renal tubular secretion via organic anion transporters (OATs), reducing uric acid excretion and increasing serum uric acid levels. This hyperuricemia can precipitate gout, especially in predisposed individuals.

**Why Each Wrong Option is Incorrect**
**Option A:** Isoniazid primarily causes hepatotoxicity and peripheral neuropathy, not hyperuricemia.
**Option B:** Rifampin induces hepatic cytochrome P450 enzymes and may cause drug interactions but does not elevate uric acid.
**Option C:** Ethambutol is linked to optic neuropathy and peripheral neuropathy, not gout.

**Clinical Pearl / High-Yield Fact**
Pyrazinamide is a key drug in short-course anti-TB regimens but should be avoided in patients with a history of gout. Monitor serum uric acid levels and consider prophylactic allopurinol in at-risk patients. Remember: **P**YRAZINAMIDE → **P**RECIPITATES **G**OUT.

**Correct Answer: C. Pyrazinamide**

✓ Correct Answer: A. Pyrazinamide