What monitoring is recommended for patients on ethambutol therapy?

• A. Daily liver function tests
• B. Renal function tests monthly
• C. No monitoring needed
• D. Baseline and periodic ophthalmologic examination including visual acuity and color vision

Answer: (D)

Ethambutol carries a notable risk of optic neuropathy, which can impair visual acuity and color vision. Because this toxicity is related to dose and duration, the appropriate approach is baseline ophthalmologic assessment before starting therapy and regular follow-up exams during treatment. Tests should focus on visual acuity and color vision, since early changes—especially in red-green color discrimination—can be the first sign of toxicity. If these changes are detected early, stopping ethambutol can prevent permanent damage, and any recovery is more likely the sooner the drug is withdrawn. This makes baseline and periodic eye examinations the essential monitoring, rather than routine liver or renal function tests for this drug.