Pyrazinamide is used exclusively in the intensive phase (first 2 months) of TB treatment. What property justifies this limited duration of use?

• A It is active only in alkaline pH environments
• B It is bactericidal only against extracellular rapidly dividing bacilli
• C It has potent sterilizing activity against semi-dormant bacilli within macrophages in acidic environments ✓
• D It is active only against rifampicin-resistant strains

Explanation

Pyrazinamide (PZA) is a prodrug activated by pyrazinamidase to pyrazinoic acid, which accumulates in the acidic pH inside macrophages. It targets semi-dormant intracellular bacilli that other drugs miss, providing potent sterilizing activity and enabling shortening of TB treatment from 9 to 6 months. Its role is confined to the initial phase because it has no role in the continuation phase where persisters are already addressed.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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