Most impoant side effect of ethambutol is:

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 ofRHZ it has been found to hasten the rate of sputum conversion and to prevent development of resistance. Loss of visual acuity I colour vision. field defects due to optic neuritis is the most impoant dose and duration of therapy dependent toxicity. Because young children ma,be unable to repo early visual impairment, it should not be used below 6 years of age. With early recognition and stoppage of therapy, visual toxicity is largely reversible. Ethambutol produces few other symptoms: nausea, rashes, fever, Neurological changes are infrequent. ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:742