MCQ on antitubercular agents: Page-1

Isoniazid, rifampicin, pyrazinamide and ethambutol are first line agents for tuberculosis. Cycloserine, tetracyclines, fluoroquinolones, macrolides, aminoglycosides,  ethionamide and p-aminosalicylic acid act as second line drugs.

Isoniazid is metabolized by N-acetylation which is variable in individual patients. Few of the patients are slow acetylators and require more time for elimination. Other group of patients act as fast acetylators producing short duration of action.

Clofazimine is a dye that produces red discoloration of skin and urine. Rifampicin also produces orange tinge to urine and saliva but it is not a dye and does not effects the skin.

Dapsone is a sulfone that acts like sulfonamides and inhibits the conversion of PABA into folic acid by inhibiting the enzyme dihydropteroate synthase. It is one of the important drug in treatment of leprosy. It is also the drug of choice in dermatitis herpetiformis which is a chronic skin disease with rashes and blistering of the skin. This disease generally coexists with celiac disease, an auto immune disorder that produces sensitivity to the gluten in diet. Dapsone produces various side effects like hemolytic anemia and allergic reactions. It increases the inflammation of leprotic lesions. Clofazimine is a dye which has anti-inflammatory effects and can antagonize the inflammatory side effects of dapsone therefore generally combined.

Isoniazid mainly produces two important side effects viz. peripheral neuropathy and hemolytic anemia. These two side effects are more pronounced in pyridoxine deficient patients and G-6-P dehydrogenase deficient patients respectively. Pyrazinamide increases uric acid levels and may predispose to gout. Rifampicin is an enzyme inducer and increases the metabolism of warfarin.