<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. The mechanism of action of E is not fully understood, but it has been found to inhibit arabinosyl transferases involved in arabinogalactan synthesis and to interfere with mycolic acid incorporation in mycobacterial cell wall Patient acceptability of E is very good and side effects are few. Loss of visual acuity / colour vision. field defects due to optic neuritis is the most impoant dose and duration of therapy dependent toxicity. Because young children may 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. Hyperuricemia is due to interference with urate excretion. ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:742 [/INST] question: Common dose dependent side effects of ethambutol is: | options: A: Red-urine B: Optic neuritis C: Nephropathy D: Peripheral neuropathy | answer: B </s>