A 4-year-old child is diagnosed with drug-susceptible pulmonary TB and has completed 2 months of intensive phase therapy with HRZE. Which drug combination should be used for the continuation phase?

Explanation

## Continuation Phase of Pediatric TB Treatment **Key Point:** After completing the 2-month intensive phase (HRZE), the continuation phase uses only 2 drugs — Isoniazid (H) and Rifampicin (R) — for 4 months in drug-susceptible TB. ### Standard 6-Month Regimen | Phase | Duration | Drugs | Frequency | |-------|----------|-------|----------| | **Intensive** | 2 months | HRZE | Daily | | **Continuation** | 4 months | HR | Daily or thrice-weekly | | **Total** | 6 months | — | — | **High-Yield:** The continuation phase omits Pyrazinamide and Ethambutol because: 1. **Intensive phase has sterilized lesions** — Pyrazinamide's role (killing intracellular bacilli in acidic pH) is complete 2. **Maintenance of cure** — Isoniazid and Rifampicin are sufficient to prevent relapse 3. **Reduced toxicity** — Ethambutol can cause optic neuritis; Pyrazinamide can cause hyperuricemia — both are unnecessary in continuation phase ### Why HR Alone Works in Continuation Phase - **Isoniazid** — Excellent intracellular penetration, sterilizes remaining bacilli - **Rifampicin** — Potent bactericidal agent, prevents relapse - Together, they maintain cure and prevent drug resistance **Clinical Pearl:** The continuation phase can be given daily or thrice-weekly (3 days per week) with equal efficacy. Thrice-weekly dosing improves adherence in resource-limited settings. **Mnemonic:** **HR** = **H**eal and **R**etain (continuation phase keeps the cure stable) **Warning:** Do NOT continue Pyrazinamide or Ethambutol into the continuation phase — they are not needed and increase the risk of adverse effects (hyperuricemia, optic neuritis, hepatotoxicity).