Ethambutol is an antimycobacterial agent used in the treatment of Tuberculosis. It is a second-line agent used in quadruple therapy with Rifampicin, Isoniazid and Pyrazinamide.
It acts by inhibiting arabinosyl transferase enzymes involved in the synthesis of cell walls in mycobacteria. Mutations in these enzymes can confer resistance.
Ethambutol is well known for its ocular side effects including optic neuritis and red-green colour blindness. Side effects are dependent on dose and duration of therapy and usually remit with drug withdrawal.
British National Formulary v.54
Brunton et al. Goodman & Gilman's The Pharmacological Basis of Therapeutics 11th edition.