Which of the following anti-tubercular drug is associated with red-green color blindness?
Correct Answer: Ethambutol
Description: Ethambutol is a synthetic, water-soluble, heat-stable compound, the dextro-isomer dispensed as the dihydrochloride salt. Ethambutol inhibits mycobacterial arabinosyl transferases, which are encoded by the embCAB operon. Arabinosyl transferases are involved in the polymerization reaction of arabinoglycan, an essential component of the mycobacterial cell wall. Resistance to ethambutol is due to mutations resulting in overexpression of emb gene products or within the embB structural gene. Hypersensitivity to ethambutol is rare. The most common serious adverse event is retrobulbar neuritis, resulting in loss of visual acuity and red-green color blindness. This dose-related adverse effect is more likely to occur at dosages of 25 mg/kg/d continued for several months. At 15 mg/kg/d or less, visual disturbances are very rare. Periodic visual acuity testing is desirable if the 25 mg/kg/d dosage is used. Ethambutol is relatively contraindicated in children too young to permit assessment of visual acuity and red-green color discrimination. Ref: Katzung Pharmacology; 12th edition; Chapter 47 Antimycobacterial Drugs; Page no: 843
Category:
Pharmacology
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