Incidence of toxic optic neuropathy with low-dose ethambutol

To investigate the incidence of ethambutol (EMB) induced optic neuropathy prescribed at a relatively low dose of ≤ 15 mg/kg/day for the treatment of tuberculosis (TB) or Mycobacterium avium complex (MAC) lung disease.

Patients diagnosed with TB or MAC lung disease received multidrug regimens including EMB at a single institution from August 2003 to July 2009. Visual monitoring was performed at baseline and at regular follow-up. The incidence of EMB-induced visual disturbances was evaluated.

Of the 415 patients included in the study, three (0.7%) developed toxic optic neuropathy over the 6-year period. Of the 289 patients prescribed a dose of ≤ 15 mg/kg/day EMB, only one (0.3%) developed toxic optic neuropathy.

The incidence of EMB-induced optic neuropathy among Koreans is estimated to be 0.7%, and can be reduced with lower doses of EMB.