Which of the following anti-tubercular drugs is most commonly associated with toxicity to the 8th cranial nerve (vestibulocochlear nerve)?

1. A

   Isoniazid

2. B

   Ethambutol

3. C

   Rifampicin

4. D

   Streptomycin

Appeared in: NORCET 10 Prelims-2026

Explanation

Listen in Hindi

• Streptomycin is an aminoglycoside antibiotic, a class of drugs known for causing ototoxicity (damage to the ear).
• This toxicity specifically targets the 8th cranial nerve, also known as the vestibulocochlear nerve.
• Damage to the vestibular part of the nerve causes balance issues like vertigo and ataxia.
• Damage to the cochlear part of the nerve causes hearing problems, such as tinnitus (ringing in the ears) and hearing loss, which can be permanent.

Why Other Options Were Wrong

• Option A: Isoniazid's primary neurotoxicity is peripheral neuropathy (damage to peripheral nerves), not ototoxicity. It is also known for causing hepatotoxicity (liver damage).
• Option B: Ethambutol's characteristic toxicity is optic neuritis, which is damage to the 2nd cranial nerve (optic nerve), leading to vision problems.
• Option C: Rifampicin is primarily associated with hepatotoxicity and causes a harmless red-orange discoloration of body fluids. It does not typically cause 8th nerve toxicity.

Related Visual

• Visual 1: Table: A summary table of first-line anti-tubercular drugs, their mechanisms of action, and their most common and serious adverse effects.
• Visual 2: Diagram: An illustration of the 8th cranial nerve, showing its two branches (vestibular and cochlear) and the inner ear structures they innervate.

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Adverse effects of anti-tubercular drugs as background academic context rather than a clinical decision trigger.
• A nurse's primary role is to monitor for adverse effects. For a patient on streptomycin, this includes asking about tinnitus, vertigo, or any changes in hearing.
• Patient education is crucial. The nurse must teach the patient to immediately report any ringing in the ears, dizziness, or hearing difficulty.
• What if? If a patient on a streptomycin-containing regimen reports new-onset ringing in their ears, the nurse must treat this as a priority. This is an early sign of ototoxicity. The nurse should withhold the next dose (if policy allows) and immediately notify the healthcare provider for further assessment and potential drug discontinuation to prevent permanent hearing loss.

How to Approach the Question

• First, identify the core of the question: it's asking for a specific adverse effect (8th cranial nerve toxicity) of a specific class of drugs (anti-tuberculars).
• This is a factual recall question. You need to access your knowledge of pharmacology.
• Systematically review each option and recall its major side effect profile.
• Isoniazid is linked to peripheral neuropathy and liver toxicity.
• Ethambutol is linked to optic neuritis (vision problems).
• Rifampicin is linked to liver toxicity and red-orange body fluids.

Concept Tested & Keywords

• Concept Tested: Adverse effects of anti-tubercular drugs
• Stem keywords: anti-tubercular drugs, toxicity, 8th cranial nerve, vestibulocochlear nerve
• Lead-in keywords: Which

Question ID

QXOEpsQh5du_qkBuLTnIrV

Copy ID