Which of the following antituberculous drugs can cause damage to the eighth cranial nerve?
A. Streptomycin
B. Isoniazid
C. Para-aminosalicylic acid
D. Ethambutol hydrochloride
Correct Answer: A. Streptomycin
Streptomycin is an aminoglycoside, and eighth cranial nerve damage (ototoxicity) is a common side effect from aminoglycosides. Ototoxicity and vestibular impairment are often thought to be the hallmark of streptomycin toxicity. In extreme cases, deafness may occur due to ototoxicity, thus caution must be exercised when combining streptomycin with other potentially ototoxic drugs.
Option B: Mild liver injury will occur in up to 20% of patients taking isoniazid. Clinical manifestations of hepatotoxicity include fever, fatigue, nausea, and vomiting. However, most patients experiencing isoniazid-induced liver injury are asymptomatic.
Option C: In one retrospective study of 7492 patients on rapidly absorbed aminosalicylic acid preparations, drug-induced hepatitis occurred in 38 patients (0.5%); in these 38 the first symptom usually appeared within three months of the start of therapy with a rash as the most common event followed by fever and much less frequently by GI disturbances of anorexia, nausea or diarrhea.
Option D: The manifestation of EMB-induced optic neuropathy appears to be from EMB’s chelation of copper. A study with 60 patients undergoing treatment with ethambutol monitored their serum copper levels. Statistical analysis confirmed there was a significant change in copper concentration, supporting the copper chelation effect by EMB.
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