The antitubercular drug safe in liver disease is: September 2011
**Core Concept**
The question tests the knowledge of antitubercular drugs, specifically their safety profiles in patients with liver disease. The underlying principle is the identification of a drug that does not require dose adjustment or has minimal hepatotoxic effects.
**Why the Correct Answer is Right**
The correct answer is Isoniazid (INH). INH is primarily metabolized by the liver, but it does not require dose adjustment in patients with mild to moderate liver disease. INH is also not hepatotoxic at therapeutic doses, making it a safer choice for patients with liver disease. INH is metabolized by the enzyme acetyltransferase, which is present in the liver. The acetylated metabolites of INH are then excreted in the urine.
**Why Each Wrong Option is Incorrect**
**Option A:** Isoniazid (INH) is not the correct answer because we are looking for a drug safe in liver disease, and INH requires dose adjustment in severe liver disease.
**Option B:** Rifampicin is not safe in liver disease because it can cause hepatotoxicity and requires dose adjustment in patients with liver disease.
**Option C:** Ethambutol is not the correct answer because it is primarily excreted unchanged in the urine and does not require dose adjustment in liver disease.
**Option D:** Pyrazinamide is not safe in liver disease because it can cause hepatotoxicity, especially when used in combination with INH.
**Clinical Pearl / High-Yield Fact**
When treating tuberculosis in patients with liver disease, it is essential to monitor liver function tests regularly and adjust the dose of INH accordingly.
**Correct Answer: A. Isoniazid (INH)**