Ethambutol induced optic neuritis: a case series

Abstract

Ethambutol is one of the first line chemotherapeutic agents used in the treatment of tuberculosis used both in the intensive and continuation phase according to the new Revised National Tuberculosis Control Program guidelines. Patient acceptability is rather good with this drug as it produces comparatively lesser adverse effects. The most important and serious side effect reported is optic neuritis, resulting in loss of visual acuity, color vision and field defects. The incidence of optic neuritis is generally directly proportional to the dose and duration of ethambutol therapy. Here we report four cases of ethambutol induced optic neuritis in patients on fixed dose combinations (FDC) of ethambutol, isoniazid, pyrazinamide and rifampicin who presented in Ophthalmology OPD in a span of 2 months, between June and July 2019. Contradictory to the rare occurrence of ethambutol induced optic neuritis this comparatively higher incidence of optic neuritis is alarming. We observed that the presentation of ethambutol induced optic neuritis can vary and dose of ethambutol along with other factors can also contribute to it. So proper pre-treatment evaluation, dosage adjustment, periodic monitoring and early detection have a significant role in prevention and treatment of ethambutol induced optic neuritis.