Ethambutol is a bacteriostatic antimycobacterial agent, classified as a first-line drug for the treatment of all forms of tuberculosis (TB). It is a synthetic, water-soluble, heat-stable compound, administered orally. Its primary clinical value lies in its ability to delay the emergence of resistance to other first-line drugs, particularly isoniazid and rifampicin, when used in combination therapy. The 1000mg strength is a standard adult dose used in the intensive phase of treatment under the Revised National Tuberculosis Control Programme (RNTCP), now known as the National Tuberculosis Elimination Programme (NTEP) in India.
Adult: 15-25 mg/kg body weight once daily. Standard NTEP/WHO recommended dose for intensive phase: 15 mg/kg/day (e.g., 1000mg for patients weighing 55-70 kg). For retreatment cases or where drug resistance is suspected: 25 mg/kg/day for first 2 months.
Note: Administer once daily, with or without food. Tablet should be swallowed whole with water. To be taken at the same time each day, preferably in the morning. Always as part of a combination regimen (e.g., with Isoniazid, Rifampicin, Pyrazinamide).
Ethambutol inhibits arabinosyl transferase enzymes (EmbA, EmbB, 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). Use only if clearly needed. Animal studies show fetal abnormalities. In active TB, benefits of treating the mother usually outweigh risks. Should be part of a standard regimen. No adequate controlled studies in pregnant women.
Driving: Caution advised. May cause dizziness, visual disturbances (blurred vision), and affect depth perception. Patients should not drive or operate machinery until visual safety is confirmed.
| Aluminum hydroxide antacids | Decreased absorption of Ethambutol by up to 20-30%. Administer at least 4 hours apart. | Moderate |
| Other neurotoxic drugs (e.g., Chloroquine, Isoniazid, Linezolid) | Increased risk of peripheral neuropathy and optic neuritis. Enhanced monitoring required. | Major |
| Allopurinol/Probenecid | May alter uric acid levels. Monitoring of serum uric acid recommended. | Moderate |
| Rifampicin | No significant PK interaction. They are used together synergistically in TB therapy. | None |
Same composition (Ethambutol (1000mg)), different brands: