skip to main content

Ethambutol Stop Immediately — SCE Infectious Diseases MCQ

Instant feedback + full explanation. One question, done properly.

EasyTuberculosisEthambutol Stop ImmediatelySCE Infectious Diseases

A 45-year-old man with TB is on standard RHZE. At week 3, he develops visual disturbance. Visual acuity has decreased from 6/6 to 6/18 bilaterally. Red-green colour vision is impaired on Ishihara testing. What is the immediate action?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Stop Ethambutol immediately — this is Ethambutol optic neuritis until proven otherwise; refer urgently to ophthalmology; visual loss is usually reversible if detected early and the drug is stopped promptly

Ethambutol causes dose-dependent retrobulbar optic neuritis. The earliest symptoms are: reduced visual acuity, impaired red-green colour discrimination (Ishihara plates), and central scotoma. Ethambutol must be STOPPED IMMEDIATELY. Referral to ophthalmology for formal assessment (visual fields, OCT) is needed. If caught early, visual loss is usually reversible over weeks to months after cessation. If continued, permanent blindness can result. Baseline visual testing (acuity and Ishihara) should be performed BEFORE starting Ethambutol and monthly during treatment.

Reference: NICE NG33 2016 – TB; BNF 2024 – Ethambutol; RCOphth 2023