Ethambutol is a unique antitubercular antibiotic which inhibits cell wall formation in Mycobacterium species. It inactivates arabinosyl transferase, an enzyme that transports mycolic acids to the Mycobacterium cell wall. It was discovered in 1961 by Lederle Labs. Ethambutol exists in three different sterioisomeric forms: the enantiomeric pair referred to as (+)-(S,S)- and (-)-(R,R)-ethambutol, along with the achiral sterioisomer called the meso-form. It is the (+)-(S,S)-enantiomer that has the antitubercular activity.
Ethambutol is slightly soluble in water.