Antitubercular — First-Line TB (RIPE Regimen, 'E') Pregnancy: Not recommended during pregnancy and in women of childbearing potential unless the potential benefit to the mother outweighs possible risks (UK SPC). Breast-feeding not recommended unless benefit to the child outweighs risks.

Ethambutol

Brand names: Myambutol

Ethambutol is a first-line antituberculous agent used in combination with other drugs for the treatment of tuberculosis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 15 mg/kg

Route: oral

Frequency: single daily dose

Dose adjusted to body weight. Adults, primary treatment and prophylaxis: single daily oral dose of 15 mg/kg, with concomitant antituberculous drugs at their recommended levels. Re-treatment: 25 mg/kg single daily dose for the first 60 days, then reduce to 15 mg/kg. Elderly: as for adults, but decreased renal function may require adjustment based on blood levels; give once daily. Renal impairment: preferably avoid; if used and creatinine clearance <30 mL/min, use 15–25 mg/kg (max. 2.5 g) three times a week with plasma ethambutol concentration monitoring.

Paediatric dose

Dose: 25 mg/kg

Route: oral

Frequency: single daily dose

Children, primary treatment and re-treatment: 25 mg/kg single daily oral dose for the first 60 days, then reduce to 15 mg/kg. For prophylaxis: single daily dose of 15 mg/kg. (US labelling states ethambutol is not recommended for pediatric patients under 13 years as safe conditions have not been established — verify against a children's formulary.)

Dose adjustments

Renal

Preferably avoid in renal impairment. If used and creatinine clearance <30 mL/min, use 15–25 mg/kg (max. 2.5 g) three times a week and monitor plasma ethambutol concentration.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Known optic neuritis and poor vision, unless clinical judgement determines it may be used

Side effects

Optic neuritis (decreased visual acuity, loss of vision, scotoma, colour blindness, visual field defect, eye pain) — uncommon
Peripheral neuropathy, numbness, paraesthesia of the extremities — rare
Hyperuricaemia — uncommon
Thrombocytopenia — rare
Rash, pruritus, urticaria — rare; severe cutaneous reactions (SJS, TEN, DRESS) reported

Interactions

Aluminium hydroxide (antacids) may impair absorption of ethambutol

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. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways