Ethambutol is a bacteriostatic antimycobacterial agent, classified as a first-line oral drug for the treatment of all forms of tuberculosis (TB). It is a critical component of Directly Observed Treatment, Short-course (DOTS) and other regimens under the Revised National Tuberculosis Control Programme (RNTCP), now known as the National Tuberculosis Elimination Programme (NTEP) in India. Its primary role is to prevent the emergence of resistance to other drugs, particularly rifampicin. The 600mg strength is a standard adult dose used in the continuation phase of treatment.
Adult: 15-25 mg/kg body weight once daily. For the 600mg tablet: Typically used for patients weighing approximately 40-55 kg in the continuation phase. Standard NTEP regimen: 600mg daily or thrice-weekly in the continuation phase.
Note: Administer once daily, with or without food. To be taken at the same time each day. Tablet should be swallowed whole with a glass of water. If gastrointestinal upset occurs, can be taken with food.
Ethambutol inhibits arabinosyl transferase enzymes (specifically EmbA, EmbB, and EmbC), which are crucial for the polymerization of cell wall arabinogalactan, a major component of the mycobacterial cell wall. This inhibition disrupts the synthesis of the mycobacterial cell wall, leading to impaired cell wall integrity and bacteriostatic activity.
Pregnancy: Pregnancy Category C (US FDA). Animal studies have shown fetal abnormalities. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is considered part of first-line TB treatment in pregnant women when required, as untreated TB poses a greater risk. Close monitoring is essential.
Driving: Patients should be cautioned that if they experience visual disturbances (blurring, changes in color vision), dizziness, or confusion, they must NOT drive or operate machinery until the symptoms are evaluated and resolved.
| Aluminum Hydroxide (Antacids) | Reduced absorption of ethambutol by forming complexes. Decreased serum levels and efficacy. | Moderate |
| Aminoglycosides (e.g., Streptomycin, Amikacin) | Additive risk of ototoxicity and nephrotoxicity. | Moderate |
| Other Neurotoxic drugs (e.g., Isoniazid, Chloroquine, Disulfiram) | Increased risk of peripheral neuropathy and optic neuritis. | Moderate to High |
| Zinc supplements | May chelate with ethambutol, potentially reducing its efficacy, though clinical significance is unclear. | Minor |