A nurse is instructing a client starting isoniazid therapy for tuberculosis. Which finding should the client report as a potential adverse effect?

• A. Nausea only
• B. Tingling in the hands
• C. Dizziness after standing
• D. Headache

Answer: (B)

Isoniazid can cause peripheral neuropathy because it depletes vitamin B6 (pyridoxine). When B6 levels drop, nerves don’t function normally, leading to numbness, tingling, or burning sensations in the hands and feet. These paresthesias are an early and telltale sign that the drug is affecting the nervous system, so reporting tingling right away allows the clinician to prevent progression by giving pyridoxine supplementation and adjusting therapy if needed.

Nausea, dizziness, or headache can occur with many medications and aren’t as specific to isoniazid’s nerve effects, so they don’t point as clearly to this potentially preventable adverse effect.