Which feature BEST distinguishes isoniazid-induced peripheral neuropathy from rifampicin-induced drug interactions in tuberculosis treatment?

Explanation

## Distinguishing Isoniazid Neuropathy from Rifampicin Drug Interactions ### Isoniazid-Induced Peripheral Neuropathy **Key Point:** Isoniazid causes a dose-dependent, reversible peripheral neuropathy due to pyridoxine (vitamin B₆) depletion and competitive inhibition of pyridoxal phosphate-dependent enzymes. **High-Yield:** This neuropathy is **completely preventable** by routine pyridoxine supplementation (10–25 mg/day), making it a key distinguishing feature. **Clinical Pearl:** The neuropathy manifests as symmetric sensory symptoms in the lower extremities, progressing to motor involvement if untreated. It is reversible upon drug discontinuation and B₆ repletion. ### Rifampicin-Induced Drug Interactions **Key Point:** Rifampicin is a potent **inducer of cytochrome P450 enzymes** (especially CYP3A4, CYP2C9, CYP2C19), leading to increased metabolism and reduced bioavailability of numerous co-administered drugs. **High-Yield:** This is a **pharmacokinetic interaction**, not a direct toxicity. It cannot be prevented by vitamin supplementation and occurs through a fundamentally different mechanism. ### Comparison Table | Feature | Isoniazid Neuropathy | Rifampicin Drug Interactions | | --- | --- | --- | | **Mechanism** | Pyridoxine depletion; direct neurotoxicity | CYP450 enzyme induction | | **Prevention** | Pyridoxine supplementation | Dose adjustment of co-drugs | | **Reversibility** | Reversible with B₆ + drug discontinuation | Reversible upon rifampicin cessation | | **Clinical Manifestation** | Peripheral neuropathy (sensory → motor) | Reduced efficacy of other drugs | | **Risk Factors** | Slow acetylators, malnutrition, alcoholism | Drug-drug interaction potential | ### Why Option 0 is Correct Isoniazid neuropathy is **uniquely preventable by pyridoxine supplementation**. This is the gold-standard discriminator because: 1. It directly addresses the mechanism (B₆ depletion). 2. Routine prophylaxis is standard of care in TB programs. 3. Rifampicin interactions cannot be prevented by vitamin supplementation. [cite:KD Tripathi 8e Ch 56]