A 28-year-old woman with newly diagnosed pulmonary TB is found to be pregnant (8 weeks gestation) at the time of TB diagnosis. Her sputum smear is positive. Which drug should be AVOIDED in her intensive phase regimen due to teratogenicity?

Explanation

## Anti-TB Drugs in Pregnancy: Safety Profile **Key Point:** Pyrazinamide is contraindicated in pregnancy due to teratogenicity and should be replaced with ethambutol in pregnant TB patients. The modified regimen becomes 2HRE/4HR (6 months total). ### Safety Profile of First-Line Anti-TB Drugs in Pregnancy | Drug | Pregnancy Safety | Rationale | FDA Category | |------|------------------|-----------|---------------| | **Isoniazid (H)** | **Safe** | No teratogenic effects; crosses placenta but not harmful | A | | **Rifampicin (R)** | **Safe** | No teratogenic effects; safe in all trimesters | C | | **Pyrazinamide (Z)** | **CONTRAINDICATED** | Teratogenic; causes fetal anomalies; avoid in pregnancy | C (relative contraindication) | | **Ethambutol (E)** | **Safe** | Safe in pregnancy; no teratogenic effects reported | B | | **Streptomycin** | **CONTRAINDICATED** | Ototoxic; causes permanent deafness in fetus; 8th nerve damage | D | **High-Yield:** The modified regimen for pregnant TB patients is **2HRE/4HR** (6 months) instead of the standard 2HRZE/4HR (6 months). Pyrazinamide is simply omitted and replaced with ethambutol. ### Why Pyrazinamide Is Contraindicated 1. **Teratogenic potential** — crosses placental barrier and may cause fetal anomalies 2. **Lack of safety data** — insufficient evidence of safety in human pregnancy 3. **Metabolite concerns** — pyrazinoic acid (metabolite) accumulates in fetal tissues 4. **WHO/Indian guidelines** — explicitly recommend avoiding pyrazinamide in pregnant TB patients **Clinical Pearl:** Despite being a highly effective drug in non-pregnant TB, pyrazinamide must be sacrificed in pregnancy to ensure fetal safety. The trade-off is a longer treatment duration (6 months instead of 6 months for standard regimen, but with reduced bactericidal activity in first 2 months). **Warning:** Do NOT confuse pyrazinamide's safety in non-pregnant patients (where it is essential) with its contraindication in pregnancy. Many students mistakenly think it is safe everywhere. **Mnemonic:** **PZ in pregnancy = PROBLEM** — Pyrazinamide is the one first-line drug that must be excluded from pregnant TB patients.