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No Pyrazinamide 9-Month Duration — SCE Infectious Diseases MCQ

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ModerateTuberculosisNo Pyrazinamide 9-Month DurationSCE Infectious Diseases

A 55-year-old man with TB develops drug-induced liver injury. Pyrazinamide is identified as the causative agent and permanently stopped. How does this affect treatment duration?

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Correct answer: B — Total treatment extends to 9 months (2RHE/7RH) — loss of Pyrazinamide from the regimen requires extending the continuation phase from 4 to 7 months to maintain cure rates

Pyrazinamide's unique sterilising activity during the first 2 months of TB treatment is the basis for the standard 6-month short-course regimen. Without Pyrazinamide, the continuation phase must be extended from 4 to 7 months (total 9 months of RHE then RH) to compensate for the reduced sterilising power. This is an important practical point — many patients develop Pyrazinamide intolerance (hepatotoxicity, gout, rash) and treatment duration adjustment is needed.

Reference: NICE NG33 2016 – TB; ATS/IDSA 2003; WHO 2022