Ethambutol therapy requires monitoring for which adverse effect?

• A. Vision changes
• B. Hearing loss
• C. Nausea
• D. Kidney pain

Answer: (A)

Ethambutol’s main adverse effect to watch for is optic nerve toxicity, which can cause vision changes. It can lead to decreased visual acuity and color vision deficits, especially red-green discrimination. Because this toxicity is related to dose and duration, you should have a baseline eye exam and ongoing visual testing during treatment, and stop or adjust the medication if vision changes occur to prevent permanent damage. The other options are not the hallmark toxicity of ethambutol: hearing loss is more typical of certain antibiotics like aminoglycosides, nausea is a nonspecific side effect seen with many drugs, and kidney pain isn’t a characteristic adverse effect of ethambutol ( though renal function should be monitored for dosing).