Myambutol (Ethambutol Hydrochloride)

Ethambutol is an antitubercular agent that interferes with the cell‑wall synthesis of Mycobacterium tuberculosis. It is employed in the following clinical situations:

• Pulmonary tuberculosis: contributes to bacterial clearance when combined with other first‑line agents.
• Extrapulmonary tuberculosis: used as part of combination therapy for disease sites such as lymph nodes or meninges.
• Multidrug‑resistant TB regimens: added to strengthen the overall antimicrobial effect in resistant cases.

• Ethambutol inhibits arabinosyl transferases that are essential for the polymerization of arabinogalactan, a key component of the mycobacterial cell wall. By blocking this biosynthetic step, the drug increases cell wall permeability, leading to impaired growth and eventual death of Mycobacterium tuberculosis.

Ethambutol may cause a range of adverse reactions, from mild to severe. Monitoring for visual changes and other symptoms is recommended.

Common Side Effects

• Nausea: mild gastrointestinal upset.
• Skin rash: localized erythema or pruritus.
• Joint pain: transient arthralgia.
• Peripheral neuropathy: tingling or numbness in extremities.
• Visual disturbances: blurred vision or color perception changes.
• Headache: mild to moderate intensity.

Serious or Rare Side Effects

• Optic neuritis: progressive loss of visual acuity and color vision, potentially irreversible.
• Severe allergic reaction: anaphylaxis, angioedema, or Stevens‑Johnson syndrome.
• Hepatic dysfunction: elevated liver enzymes or hepatitis.
• Seizures: rare central nervous system involvement.
• Acute renal failure: abrupt decline in kidney function.

Ethambutol requires careful patient monitoring and appropriate use conditions.

• Visual monitoring: baseline and periodic eye examinations are essential.
• Renal function: adjust dose in patients with impaired kidney function.
• Hepatic status: use cautiously in those with liver disease.
• Hypersensitivity: discontinue if allergic reactions occur.
• Pregnancy and lactation: safety not established; evaluate risk‑benefit.
• Store at ambient temperature: keep in the original container, protect from moisture and direct sunlight.

Ethambutol can interact with several medicines, influencing efficacy or toxicity.

Major Interactions (Avoid)

• Other optic‑toxic agents (e.g., linezolid, chloramphenicol): increased risk of vision loss.
• Nephrotoxic drugs (e.g., aminoglycosides, vancomycin): additive kidney injury.

Moderate Interactions (Monitor Closely)

• Rifampicin: may reduce ethambutol plasma concentrations.
• Isoniazid: potential increase in peripheral neuropathy risk.
• Pyrazinamide: combined hepatotoxic potential.
• Antacids containing aluminum or magnesium: may impair absorption.