antibioticsbooks

Ethambutol
25
Agent: ethambutol (EMB)
Ethambutol is a first-line drug for the treatment
of both active tuberculosis and MAC infections. It
inhibits production of arabinogalactan, a component
of the mycobacterial cell wall. Like pyrazinamide,
ethambutol is principally used in the initial
four-drug phase of active tuberculosis, but it is usually
given for the duration of MAC therapy.
Mechanism of Action
Ethambutol inhibits the enzyme aribinosyl transferase
III, which blocks production of arabinogalactan.
Because arabinogalactan is a component
of the cell wall of mycobacteria but not “typical”
bacteria, the microbial activity of ethambutol is
limited to mycobacteria.
Spectrum
M. tuberculosis, M. avium-intracellulare complex,
M. kansasii
Adverse Effects
The characteristic adverse effect of ethambutol
is optic neuritis, often manifesting as decreased
visual acuity or the inability to differentiate
red from green. It is dependent on both the