<s>[INST] context: Ethambutol (E): Ethambutol is selectively tuberculostatic and clinically as active as S. Fast multiplying bacilli are more susceptible as are many atypical mycobacteria. Added to the triple drug regimen of RHZ it has been found to hasten the rate of sputum conversion and to prevent development of resistance. About 3 / 4 of an oral dose of E is absorbed. It is distributed widely but penetrates meninges incompletely and is temporarily stored in RBCs Less than 1/2 of E is metabolized. It is excreted in urine by glomerular filtration and tubular secretion; plasma half life is 4 hrs. Caution is required in its use in patients with renal disease. Patient acceptability of E is very good and side effects are few. Pyrazinamide (Z): Chemically similar to INH It is more lethal to intracellularly located bacilli and to those at sites showing an inflammatory response (pH is acidic at both these locations). It is highly effective during the first 2 months of therapy when inflammatory changes are present Hepatotoxicity is the most impoant doserelated adverse effect. R ifampin (Rifampicin, R): Adverse effects: The incidence of adverse effects is similar to INH. Hepatitis, a major adverse effect, generally occurs in patients with preexisting liver disease INH: Hepatitis, a major adverse effect of iNH, is rare in children, but more common in older people and in alcoholics. It is due to dose-related damage to liver cells and is reversible on stopping the drug. Other side effects are rashes, fever, acne and ahralgia ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:741,742 [/INST] question: Which of the following antitubercular drugs is safe in hepatitis? | options: A: Isoniazid B: Rifampicin C: Pyrazinamide D: Ethambutol | answer: D </s>