Drug Detail

Ethambutol

Last Updated June 10, 2016

Trade Names

Drug Classification

Antimycobacterial

Formulations

Indications and Pharmacology

Indication: treatment of primary tuberculosis in combination with other antituberculosis drugs.

Mechanism of action: inhibits formation of the bacterial cell wall; bacteriostatic but may be bacteriocidal at high doses.

Pharmacokinetics: well absorbed from gastrointestinal tract and widely distributed throughout body; half-life 3-4 hours, prolonged with renal failure.

Dosage

Adult Dose: 15-20 mg/kg/day in single dose for 2 months.

Geriatric Dose: should not exceed 15 mg/kg/day.

May be taken with food.

Use in Renal or Hepatic Insufficiency: 

  • For renal insufficiency, prolong dose intervals. Glomerular filtration rate 10-50 mL/min: 24-36 hours; glomerular filtration rate < 10 mL/min: 48 hours.
  • No adjustments needed for hepatic insufficiency.

Use in Pregnancy and Breastfeeding: Pregnancy Category B; dose not to exceed 15 mg/kg/day. No association with congenital abnormalities.

Excreted in breast milk; no reported effects on nursing infants.

Use in Children: 15-25 mg/kg/day in single dose for 2 months.

Warnings

Contraindicated in patients with hypersensitivity to ethambutol, patients with known optic neuritis, and patients with advanced renal failure.

May reduce visual acuity, and irreversible blindness has been reported.

Vision should be monitored regularly and changes reported immediately; examination should include ophthalmoscopy, finger perimetry and colour discrimination testing.

Hepatotoxicity has been reported.

Drug–Drug Interactions

Pyrazinamide and diuretics (eg, thiazides): potential for additive elevation of serum urate.

Neurotoxic agents: increased risk of optic or peripheral neuritis.

Antacids containing aluminium hydroxide: reduced ethambutol absorption; avoid within 4 hours of ethambutol administration.*

Considerations for Special Populations

Paediatric: extra caution warranted for patients < 8 years of age due to difficulty of monitoring visual symptoms; should be used in children with advanced HIV, severe pulmonary or extrapulmonary tuberculosis, or with infections resistant to other drugs (off label).

Geriatric: use lower dosage range due to decreased renal function; not to exceed 15 mg/kg/day.

Adverse Effects

Dose-dependent ocular toxicity, decreases in visual acuity, including irreversible blindness, due to unilateral or bilateral optic neuritis; hyperuricemia associated with arthralgia, precipitation of acute gout, gastrointestinal disturbances, peripheral neuropathy, skin rashes and dermatitis, dizziness, confusion, thrombocytopenia, renal toxicity, hepatitis.

*Information from Aurum Institute Drugs on the Go.