OCULAR TOXICITY FROM ETHAMBUTOL - A REVIEW OF 4 CASES AND RECOMMENDEDPRECAUTIONS

Aims. To document the clinical and demographic features of cases of et hambutol ocular toxicity, to review the literature on this subject and to critically review current guidelines for ethambutol administration . Methods. Cases of ocular toxicity from ethambutol were sought retros pectively at Green Lane and Wellington Hospitals between 1992 and 1995 . The records of cases identified were examined. Results. Four subject s with tuberculosis developed ocular toxicity 2(1/2), 7(1/2), 8 and 12 months after starting ethambutol. Normal visual acuity returned in th ree cases; one patient has severe, permanent visual impairment. Langua ge difficulties were present in three subjects. Conclusions. Impaired communication was potentially very important in this series. Special c are is needed in educating patients about ethambutol. We propose addit ional recommendations: 1. the usual daily dose of ethambutol should be 15 mg/kg/day, not 25 mg/kg/day; using 25 mg/kg/day (or lesser doses i n the presence of renal impairment) should prompt regular formal ophth almological evaluation (e.g. monthly) in cases with comprehension or c ommunication difficulties; 3. both ethambutol and isoniazid should be stopped immediately if severe optic neuritis occurs. Isoniazid should be stopped if less severe optic neuritis does not improve within six w eeks after stopping ethambutol.