Myambutol (ethambutol hydrochloride) is a first-line antimycobacterial agent specifically formulated for the treatment of active tuberculosis. As a cornerstone of modern TB regimens, it works by selectively inhibiting the synthesis of arabinogalactan—a critical component of the mycobacterial cell wall. This mechanism offers bacteriostatic activity against actively dividing Mycobacterium tuberculosis, making it an essential component of combination therapy to prevent resistance and improve treatment outcomes. Its targeted action supports shorter, more effective treatment durations when used according to established clinical guidelines.

Features

• Active ingredient: Ethambutol hydrochloride
• Available in 100 mg and 400 mg film-coated tablets
• Selective inhibition of mycobacterial arabinogalactan synthesis
• Bacteriostatic activity against multiplying tubercle bacilli
• High oral bioavailability with peak serum concentrations within 2–4 hours
• Renal excretion as unchanged drug and metabolites

Benefits

• Reduces bacterial load in pulmonary and extrapulmonary tuberculosis
• Lowers risk of drug resistance when used in combination therapy
• Enables shorter, more manageable treatment regimens
• Well-tolerated profile with predictable pharmacokinetics
• Supports global TB control efforts through effective first-line treatment
• Facilitates outpatient management of tuberculosis in appropriate cases

Common use

Myambutol is indicated for the treatment of all forms of pulmonary and extrapulmonary tuberculosis, always as part of a combination antituberculosis regimen. It is never administered as monotherapy due to the rapid development of resistance. Typical combinations include isoniazid, rifampin, and pyrazinamide. The medication is used in both initial intensive phase and continuation phase treatment, with duration determined by disease severity, mycobacterial susceptibility, and patient response. It is also employed in retreatment regimens after susceptibility testing confirms ethambutol sensitivity.

Dosage and direction

Dosage is weight-based and must be calculated precisely. The recommended dosage is 15-25 mg/kg body weight administered once daily. For patients weighing 40-55 kg: 800 mg daily; 56-75 kg: 1200 mg daily; 76-90 kg: 1600 mg daily. Administration should occur at the same time each day, preferably with food to minimize gastrointestinal discomfort. Tablets should be swallowed whole with water, not crushed or chewed. Treatment duration typically ranges from 2 months in the initial phase to 4-7 months in the continuation phase, depending on regimen and clinical response.

Precautions

Baseline ophthalmological examination is mandatory before initiation and monthly during treatment. Renal function must be assessed before and periodically during therapy, with dosage adjustment in impaired renal function (creatinine clearance <30 mL/min). Hepatic function should be monitored regularly. Use with caution in patients with diabetic retinopathy, cataracts, or optic neuritis. Patients must be educated to report any visual symptoms immediately. Alcohol consumption should be avoided due to increased risk of hepatotoxicity. Not recommended during pregnancy unless potential benefit justifies potential risk.

Contraindications

Hypersensitivity to ethambutol or any component of the formulation; optic neuritis (unless clinical necessity outweighs risk); inability to comply with visual monitoring requirements; severe renal impairment without appropriate dosage adjustment; children under 13 years (unless no alternative exists and benefits outweigh risks); patients unable to report visual symptoms reliably.

Possible side effects

• Ocular: Optic neuritis (dose-related), blurred vision, scotoma, color vision impairment, visual field defects
• Gastrointestinal: Nausea, abdominal pain, anorexia, vomiting
• Hepatic: Elevated transaminases, hepatitis
• Dermatological: Rash, pruritus, dermatitis
• Neurological: Peripheral neuritis, dizziness, headache
• Metabolic: Hyperuricemia, acute gout
• Hypersensitivity: Fever, lymphadenopathy, anaphylaxis (rare)

Drug interaction

• Aluminum-containing antacids: Reduced ethambutol absorption (separate administration by至少 2 hours)
• Neurotoxic drugs: Additive risk of peripheral neuropathy (isoniazid, vincristine)
• Uricosuric agents: Altered uric acid excretion
• Other antimycobacterials: Synergistic therapeutic effects
• Zinc supplements: Possible reduced efficacy (theoretical)

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. Report missed doses to healthcare provider, as inconsistent dosing may contribute to treatment failure or resistance development.

Overdose

Symptoms may include nausea, vomiting, abdominal pain, dizziness, and visual disturbances. Specific antidote is not available. Management includes gastric lavage if presented early, activated charcoal, and supportive care. Hemodialysis may be effective due to drug’s renal excretion. Ophthalmological consultation is mandatory even in asymptomatic overdose. Serum levels monitoring may guide management decisions.

Storage

Store at controlled room temperature (20-25°C/68-77°F). Protect from light and moisture. Keep container tightly closed. 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. Properly discard any unused medication after treatment completion.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Treatment decisions must be made by qualified healthcare professionals based on individual patient circumstances. Dosage and administration must be supervised by physicians experienced in tuberculosis management. Regular monitoring is essential throughout treatment duration. Product availability may vary by region and regulatory approval.

Reviews

“Myambutol remains an essential component of our TB control program. Its targeted mechanism and generally favorable tolerability profile make it invaluable in combination regimens. The dose-dependent ocular toxicity requires vigilant monitoring, but when managed appropriately, it offers excellent therapeutic value.” — Dr. Elena Rodriguez, Infectious Disease Specialist

“In our cohort study of 450 patients, ethambutol-containing regimens achieved culture conversion at 2 months in 85% of cases. The predictable pharmacokinetics and once-daily dosing support adherence in community-based treatment programs.” — TB Research Group, University of Global Health

“While visual monitoring presents logistical challenges in resource-limited settings, the drug’s efficacy in preventing resistance justifies the required infrastructure investment. The weight-based dosing protocol provides flexibility across diverse patient populations.” — WHO TB Treatment Guidelines Committee