Question

A 35 year old pilot has been detected to have pulmonary tuberculosis. Which one of the following should NOT be prescribed for him?

• A. Isoniazid
• B. Ethambutol
• C. Pyrazinamide
• D. Streptomycin

Hint:

Think about which anti TB drug affects color vision.

Answer 1

The Correct Option is B

Step 1: Understanding the Question.
A pilot needs sharp, reliable vision for his job. The question asks which anti tuberculosis drug should be avoided in him.

Step 2: Key Concept.
Ethambutol can damage the optic nerve, a side effect called optic neuritis. It can blur vision and, more specifically, weaken the ability to tell red from green, known as retrobulbar neuritis with red green color blindness.

Step 3: Detailed Explanation.
Isoniazid mainly risks nerve damage in the limbs, called peripheral neuropathy, and liver toxicity, not eye problems, so it is safe to continue in a pilot.
Ethambutol carries a real risk of optic neuritis and red green color vision loss. A pilot depends on perfect color vision and clear sight to read instrument panels and signals, so this drug is unsafe for him even though it is a standard first line TB drug for most patients.
Pyrazinamide mainly risks liver toxicity and joint pain from raised uric acid, not vision.
Streptomycin mainly risks damage to hearing and balance, called ototoxicity, and kidney toxicity, not vision.

Step 4: Final Answer.
Ethambutol should not be prescribed for this pilot because of its risk to color vision and the optic nerve.