Walsh & Hoyt: Ethambutol

Of the drugs in wide use at the time this chapter was compiled, ethambutol is undoubtedly the one most often implicated in toxic optic neuropathy. The potential for visual impairment was recognized soon after this antituberculous agent was introduced. The original formulation was a racemic mixture. However, when it was discovered that the D-form was predominantly responsible for the therapeutic effect and the L-form for the toxicity, the L-form was withdrawn from the market.