Ethambutol
Brand names: Myambutol
Ethambutol is a first-line antituberculous agent used in combination with other drugs for the treatment of tuberculosis.
ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.
Clinical monograph
How it works
It inhibits arabinosyl transferases involved in mycobacterial cell wall (arabinogalactan) synthesis, exerting a bacteriostatic effect on Mycobacterium tuberculosis.
Prescribing in practice
- Dose-related optic neuritis is the key toxicity, causing reduced visual acuity and red-green colour blindness, so visual function must be assessed and patients warned to report any visual change immediately.
- It is always used as part of combination therapy to prevent emergence of resistance, never as a single agent.
- Dose adjustment is needed in renal impairment because it is largely renally excreted.
Monitoring
Assess visual acuity and colour vision before and during treatment, and monitor renal function.
Counselling the patient
- Report any change in vision, including blurring or difficulty distinguishing colours, straight away.
- Take all your tuberculosis medicines together as prescribed and do not miss doses.
- Complete the full course even when you feel better.
Evidence & guidelines
Ethambutol is a standard component of the four-drug regimen in NICE tuberculosis guidance (NG33).
Reference: NICE NG33 (TB Management); PHE TB Treatment Guidelines; WHO TB Treatment Guidelines 2022; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).
Related
Curated clinical cross-links plus same-class fallbacks.