Ethambutol

Ethambutol is an antibiotic that belongs to a class of medicines known as anti tuberculosis drugs. It is used in the treatment and prevention of tuberculosis, an infectious disease that mainly affects the lungs and in some cases other parts of the body.

Ethambutol is usually given in combination with at least one other tuberculosis medicine. It should be used in the dose and duration as advised by your doctor. This medicine may be taken with or without food, preferably at the same time every day.

• Pulmonary Tuberculosis: Used for the treatment of pulmonary tuberculosis. Should not be used as the sole antituberculous drug, but should be used in conjunction with at least one other antituberculous drug.
• Extrapulmonary Tuberculosis: Used for the treatment of tuberculosis outside the lungs.

Anti-tubercular antibiotics

Anti-tuberculosis Agent (Bacteriostatic)

Ethambutol appears to inhibit the synthesis of 1 or more metabolites in susceptible bacteria resulting in impairment of cellular metabolism, arrest of multiplication, and cell death. It is active against susceptible bacteria only when they are undergoing cell division.

Ethambutol interferes with RNA synthesis, causing suppression of Mycobacteria multiplication. It also has bacteriostatic action against M tuberculosis by acting on rapidly growing pathogens in cavity walls and is also effective in slow-growing pathogens.

Adult Dose (Oral):

• Initial treatment (no prior therapy): 15 mg/kg/day or 30 mg/kg thrice weekly (with isoniazid, rifampicin and pyrazinamide).
• Retreatment (history of antimycobacterial therapy): Initial: 25 mg/kg/day for 60 days, then reduce to 15 mg/kg/day.

Child Dose: 15-25 mg/kg, max 2.5 g q24h; Drug-resistant TB: 15-25 mg/kg daily or 50 mg/kg twice weekly.

Renal Dose: Dose adjustment may be needed as determined by blood levels.

Take this medicine in the dose and duration as advised by your doctor. Swallow it as a whole. Do not chew, crush or break it. Ethambutol may be taken with or without food, but it is better to take it at a fixed time.

If you miss a dose of Ethambutol, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular schedule. Do not double the dose.

Common Side Effects:

• Visual impairment
• Color blindness (green-red color blindness)
• Retrobulbar neuritis
• Constriction of visual field
• Central or peripheral scotoma

Other Side Effects:

• Confusion, disorientation, hallucinations
• Headache, dizziness, malaise
• Jaundice or transient liver dysfunction
• Peripheral neuropathy
• Thrombocytopenia
• GI disturbances (nausea, vomiting, anorexia, abdominal pain)
• Allergic reactions (rash, pruritus, fever)

Precautions:

• Ethambutol may cause sight problems and tingling or numbness in hand or feet; do not drive until you know how it affects you.
• It has to be taken for several months in order for it work properly (usually 6 months).
• Take with food to avoid stomach upset.
• Can lower blood sugar; monitor blood sugar regularly if diabetic.
• Your doctor may monitor liver function, vision and thyroid function.
• Do not stop taking even if you start to feel better (early stopping can lead to treatment failure and drug-resistant TB).
• Caution in patients with ocular defects, renal impairment.

Contraindications:

• Hypersensitivity
• Optic neuritis
• Lactation
• Patients unable to appreciate and report visual side effects

Drug Interactions:

• Aluminium hydroxide: Delayed or reduced absorption.
• Neurotoxic agents: Caution required.

Food Interactions: It is not known whether it is safe to consume alcohol with Ethambutol. Consult your doctor.

Use in Pregnancy: Category C. Animal studies have shown adverse effects on the fetus. Should be used only if potential benefit justifies potential risk to the fetus.

Use in Lactation: Ethambutol is safe to use during breastfeeding. Human studies suggest that the drug does not pass into breastmilk in significant amount and is not harmful to the baby.

Pediatric Use: Not recommended for use in children under 13 years (safe conditions for use not established).

Geriatric Use: No specific dosage adjustment is necessary for elderly patients.

Renal Impairment: Use with caution; dose adjustment may be needed as determined by blood levels. Kidney function tests advisable before start.

Hepatic Impairment: Use with caution; dose adjustment may be needed.

Overdose: Overdose may cause visual impairment. In case of overdose, symptomatic treatment should be given and seek immediate medical attention.

Storage: Store between 20-25 degree C. Protect from light, moisture and excessive heat.

Ethambutol