MCQ MAHE 2000 Pharmacology Answer 08

The Correct Answer is C

Isoniazid, rifampin, ethambutol, streptomycin, and pyrazinamide are the principal or so-called "first line" drugs for tuberculosis because of their efficacy and acceptable degree of toxicity.

Ethambutol is bacteriostatic and specific for most strains of Mycobacterium tuberculosis and Mycobacterium kansasii. Resistance is not a serious problem if the drug is employed with other antituberculous agents. Ethambutol can be used in combination with pyrazinamide, isoniazid, and rifampin to treat tuberculosis. Its mechanisms of action are unknown.

Absorbed on oral administration, ethambutol is well distributed throughout the body. It is concentrated in erythrocytes. Penetration into the central nervous system is therapeutically adequate in tuberculous meningitis. Both parent drug and metabolites are excreted by glomerular filtration and tubular secretion.

The most important adverse effect is optic neuritis, which results in diminished visual acuity and loss of ability to discriminate between red and green. Visual acuity should be periodically examined. Discontinuation of the drug results in reversal of the toxic symptoms. In addition, urate excretion is decreased by the drug, thus gout may be exacerbated.

Category: MAHE 2000 MCQs