Anti tubercular drug contraindicated in pregnancy is –
**Core Concept**
Isoniazid, a first-line antitubercular medication, is used to treat Mycobacterium tuberculosis infections. However, its safety profile in pregnancy is a concern due to potential teratogenic effects.
**Why the Correct Answer is Right**
Isoniazid is contraindicated in pregnancy due to its risk of causing hepatotoxicity and potential teratogenic effects. The enzyme N-acetyltransferase 2 (NAT2) plays a crucial role in metabolizing isoniazid, and genetic variations in this enzyme can affect its clearance and increase the risk of hepatotoxicity. Additionally, isoniazid can cross the placenta and potentially cause fetal harm.
**Why Each Wrong Option is Incorrect**
* **Option A:** Rifampicin is actually considered relatively safe in pregnancy and is often used as a first-line antitubercular medication. However, it can cause fetal hemolysis and is best avoided in the first trimester.
* **Option B:** Ethambutol is generally considered safe in pregnancy but can cause optic neuritis, which may be a concern in certain cases. However, it is not the primary contraindicated antitubercular medication in pregnancy.
* **Option C:** Pyrazinamide is also considered relatively safe in pregnancy but can cause hepatotoxicity, similar to isoniazid. However, it is not the primary contraindicated antitubercular medication in pregnancy.
**Clinical Pearl / High-Yield Fact**
It's essential to note that antitubercular medications should be carefully managed in pregnant women, and the risks and benefits of each medication should be weighed individually. A thorough discussion with the patient, including the potential risks and benefits, is crucial before initiating treatment.
**Correct Answer:** D. Isoniazid is contraindicated in pregnancy due to its risk of causing hepatotoxicity and potential teratogenic effects.