Ethambutol-Induced bilateral retrobulbar neuritis with cecocentral scotoma in cervical tuberculous lymphadenitis patient: A case report with estimated plasma level consideration

Ethambutol is considered to be safest first-line antitubercular drug, and patient acceptability is rather good in both intensive and continuation phase of the tuberculosis treatment with daily regimen. The important adverse effect associated with ethambutol 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 and rarely reported in a low standard dose. Here, we report a case of a 40-year-old female patient with complaints of progressive diminished vision (especially during day time) with a low daily dose (15 mg/kg/day) of ethambutol. She got diagnosed with cervical tuberculous lymphadenitis and was receiving isoniazid, rifampicin, ethambutol, and levofloxacin. In rare instances, ethambutol ocular toxicity may present with cecocentral scotoma. In rare instances, plasma levels are performed. An estimated plasma level of ethambutol was found to be in higher end (5.6 μg/ml) of the reported therapeutic range (2–6 μg/ml). Bilateral retrobulbar neuritis with cecocentral scotoma adverse effect due to ethambutol can be seen in plasma therapeutic range.