Mechanism of Action
Ethambutol inhibits the enzyme arabinosyl transferase IIIZ , 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
Disruption of arabinoglycan alters the cell barrier , enhancing the activity of lipophilic drugs such as Rifampin & ofloxacin
Therapeutic uses:
Ethambutol has no effect on organisms other than mycobacteria.
- In combination with ISONIAZID and Rifampin.
- It may be used with ISONIAZID or alone during pregnancyZ , as it is least toxic.
Adverse effects:
- Visual disturbance e.g. optic neuropathies, often manifesting as decreased visual acuity or the inability to differentiate red from green. The occurrence of this adverse effect is dependent on both the dose and duration of therapy It is not recommended for routine use in children too young to permit assessment of visual acuity & red- green color discrimination
- Hyperuricaemia and gout due to decreased renal excretion of uric acid
- Mild GIT upset, malaise fever, rash, headache and peripheral neuritis