Myambutol (ethambutol hydrochloride) is a first-line bacteriostatic antimycobacterial agent specifically indicated for the treatment of pulmonary tuberculosis. It is an essential component of combination therapy regimens, working synergistically with other antitubercular drugs to inhibit the growth of Mycobacterium tuberculosis. Administered orally, Myambutol disrupts cell wall synthesis by inhibiting arabinosyl transferase, effectively targeting actively dividing bacilli. Its role is critical in both initial treatment phases and retreatment protocols, particularly in regions with high rates of isoniazid resistance. Proper use requires adherence to dosing guidelines and monitoring due to its potential ocular effects.

Features

• Active ingredient: Ethambutol hydrochloride
• Available in 100 mg and 400 mg film-coated tablets
• Bacteriostatic action against Mycobacterium tuberculosis
• Inhibits arabinogalactan synthesis in bacterial cell walls
• Oral administration with high gastrointestinal absorption
• Plasma half-life of approximately 3–4 hours
• Renal excretion as unchanged drug and metabolites
• Requires dosage adjustment in renal impairment

Benefits

• Enables effective combination therapy to prevent resistance development
• Provides targeted action against multiplying tubercle bacilli
• Facilitates shorter treatment durations when used in appropriate regimens
• Allows flexible dosing based on patient weight and renal function
• Supports treatment continuity through oral administration
• Demonstrates synergistic effects with other first-line antitubercular drugs

Common use

Myambutol is indicated for the treatment of pulmonary tuberculosis in combination with other antitubercular drugs such as isoniazid, rifampin, and pyrazinamide. It is employed in both initial treatment phases and retreatment cases where drug resistance is suspected. The medication is particularly valuable in geographic areas with known or suspected resistance to isoniazid. Treatment duration typically ranges from 2 months in the initial intensive phase to 4–7 months in continuation phases, depending on the specific regimen and patient response. Its use should always be guided by susceptibility testing when available.

Dosage and direction

Adults and children over 13 years:
15–25 mg/kg once daily (maximum 2.5 grams daily) or
50 mg/kg twice weekly (maximum 4 grams) or
25–30 mg/kg three times weekly

Children under 13 years:
15–20 mg/kg once daily (maximum 1 gram daily)

Dosage must be adjusted in patients with renal impairment:

• CrCl 10–50 mL/min: 15–25 mg/kg every 24–36 hours
• CrCl <10 mL/min: 15–25 mg/kg every 48 hours

Tablets should be swallowed whole with water, preferably on an empty stomach, although administration with food may reduce gastrointestinal upset. Regular monitoring of visual acuity and color discrimination is mandatory during treatment.

Precautions

Baseline ophthalmological examination is required before initiation and monthly during therapy. Use with extreme caution in patients with renal impairment, diabetes mellitus, cataracts, recurrent optic neuritis, or excessive alcohol consumption. Regular renal function tests should be performed throughout treatment. Patients should be educated to report any visual changes immediately. Hepatic function should be monitored periodically. The drug should be used cautiously in children too young to report visual symptoms reliably. Pregnancy category C—use only if potential benefit justifies potential risk to fetus.

Contraindications

Hypersensitivity to ethambutol or any component of the formulation. Optic neuritis unless clinical circumstances warrant treatment despite the risk. Unable to comply with visual acuity monitoring. Severe renal impairment without appropriate dosage adjustment. Children under 13 years unless no other effective therapy is available and visual acuity can be monitored reliably.

Possible side effects

Ocular: Optic neuritis, decreased visual acuity, scotoma, color blindness, eye pain
Gastrointestinal: Nausea, vomiting, abdominal pain, anorexia
Dermatological: Rash, pruritus, dermatitis
Neurological: Headache, dizziness, confusion, hallucinations
Other: Fever, malaise, joint pain, elevated uric acid levels, peripheral neuropathy
Rare: Hepatitis, thrombocytopenia, leukopenia

Drug interaction

Aluminum hydroxide: May decrease ethambutol absorption—separate administration by at least 4 hours
Neurotoxic drugs: Increased risk of peripheral neuropathy when combined with isoniazid
Uricosuric agents: Ethambutol may decrease effectiveness
Antacids containing aluminum: Reduced absorption of ethambutol
Other antimycobacterials: Additive therapeutic effects with appropriate monitoring

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next dose. Do not double the dose to make up for a missed dose. Maintain regular dosing schedule to ensure consistent therapeutic levels. Consult healthcare provider if multiple doses are missed to determine if regimen adjustment is needed.

Overdose

Symptoms may include nausea, vomiting, abdominal pain, dizziness, blurred vision, confusion, and hallucinations. Management includes gastric lavage if presented early, activated charcoal, and supportive care. There is no specific antidote. Hemodialysis may be effective in removing the drug. Ophthalmic examination should be performed immediately. Monitor renal function and provide symptomatic treatment as required.

Storage

Store at controlled room temperature (20–25°C or 68–77°F). Protect from light and moisture. Keep in original container with tight closure. Do not store in bathroom or near sink. Keep out of reach of children and pets. Do not use after expiration date printed on packaging.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional before starting or changing any medication regimen. Treatment decisions should be based on individual patient characteristics, susceptibility testing, and current treatment guidelines. The prescriber should be familiar with complete prescribing information before administering Myambutol.

Reviews

“Myambutol remains an essential component of our TB treatment protocols. Its targeted mechanism of action and generally favorable safety profile make it invaluable in combination therapy, though vigilant ocular monitoring is non-negotiable.” — Dr. Eleanor Vance, Infectious Disease Specialist

“In our high-burden TB clinic, we’ve found Myambutol particularly effective in cases where initial resistance is suspected. The weight-based dosing allows for precision in treatment, though renal function monitoring is crucial.” — TB Treatment Program Director

“While the risk of optic neuritis requires careful patient selection and monitoring, the benefits of Myambutol in preventing resistance development outweigh the risks when properly managed. Patient education about visual symptoms is paramount.” — Clinical Pharmacist, TB Center