Toxic ocular effects of ethambutol.
Ethambutol hydrochloride has been used in the treatment of tuberculosis for 25 years. Its only important adverse effect, retrobulbar neuritis, is thought to be a minor concern with conventional dosages. The author presents four cases of serious visual impairment due to ethambutol therapy. Three of the patients were receiving a maintenance dosage of 15 mg/kg per day. The fourth patient was inadvertently given 25 mg/kg per day for 4 months. After therapy with the drug was stopped, improvement was slow, with complete recovery in two cases and only minor residual changes in a third. The patient who received the higher dosage of ethambutol suffered permanent, marked impairment. Ethambutol appears to contribute little to modern short-course antituberculous regimens that include more potent agents such as isoniazid and rifampin. In view of this and the potential for serious visual impairment, alternative antituberculous agents should be considered.
D000328:Adult; D000368:Aged; D004341:Drug Evaluation; D004977:Ethambutol / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009902:Optic Neuritis / Q000139:chemically induced*; D012607:Scotoma / Q000139:chemically induced; D013997:Time Factors; D014792:Visual Acuity / Q000187:drug effects
D004977:Ethambutol