Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 7 Sept 2026Clinical review pending
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Stop suspected ethambutol toxicity and seek urgent review
New reduced central vision or altered colour perception during ethambutol treatment can indicate optic nerve toxicity. Waiting for visible disc pallor or a routine appointment can allow further damage.
Action: Stop ethambutol immediately pending urgent ophthalmic assessment and contact the TB team the same day to organise the antimicrobial plan. Record the last dose, renal function, acuities and symptoms; do not independently stop the entire multidrug regimen.
Synopsis
Detect medication-related optic nerve injury early, interpret visual testing limitations, and coordinate withdrawal or replacement treatment while preserving control of the underlying infection.
Ask about visual symptoms at every ethambutol treatment visit and explain the action required before symptoms occur.
A normal-looking optic disc does not exclude early toxic dysfunction.
Test each eye separately because the two eyes can be affected unequally.
Key red flags
A patient taking ethambutol reports new washed-out colours or difficulty reading.
Investigation priorities
01
Monocular acuity and colour testingFirst step
Quantify functional change against previous measurements where available.
Management branches
Before treatmentMake visual safety part of the prescribing plan
Ethambutol is being started or transferred to another prescribing service.
Establish relevant eye disease and arrange the agreed pretreatment assessment, documenting each eye's acuity and colour performance.
Review actual weight, renal function and the intended dose and duration with the TB prescribing team.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 7 Sept 2026; clinical approval remains outstanding.