The antitubercular drug safe in liver disease is: September 2011

Ans. C: Ethambutol Approximately 50% of the oral dose of Ethambutol is eliminated unchanged in the urine within 24 hours; 15% of the drug is excreted in the form of 2 metabolites Its serious toxicity is ocular Ethambutol/ EMB/ E It is a bacteriostatic antimycobacterial drug Adverse effects of ethambutol are: - Optic neuritis: Hence contraindicated in children below 6 yrs of age. - Red-green color blindness - Peripheral neuropathy - Ahralgia - Hyperuricaemia - Veical nystagmus - Milk skin reaction Ethambutol is bacteriostatic against actively growing TB bacilli. It works by obstructing the formation of cell wall. Mycolic acids attach to the 5'-hydroxyl groups of D-arabinose residues of arabinogalactan and form mycolylarabinogalactan-peptidoglycan complex in the cell wall. It disrupts arabinogalactan synthesis by inhibiting the enzyme arabinosyl transferase. Disruption of the arabinogalactan synthesis inhibits the formation of this complex and leads to increased permeability of the cell wall It is well absorbed from the gastrointestinal tract and well distributed in body tissues and fluids, 50% is excreted unchanged in urine.