A 35-year-old man on isoniazid for TB exposure has weekend drinking and heavy smoking. Which adverse reaction should you alert him to report immediately?

A 35-year-old man on isoniazid for TB exposure has weekend drinking and heavy smoking. Which adverse reaction should you alert him to report immediately?

• A. Numbness and tingling in the feet.
• B. Severe vision changes.
• C. Severe abdominal pain.
• D. Joint swelling.

Answer: (A)

Peripheral neuropathy from isoniazid occurs because the drug disrupts pyridoxine (vitamin B6) metabolism, leading to deficiency that impairs nerve function. Alcohol use makes this risk worse, so numbness, tingling, or other paresthesias in the feet (and sometimes hands) are a key warning sign. Reporting these symptoms promptly allows timely pyridoxine supplementation and adjustments if needed to prevent progression. Other adverse effects, such as vision changes (more linked to another TB drug) or abdominal pain from hepatotoxicity, are important but the described sensory symptoms are the classic early signal to address immediately.

Peripheral neuropathy from isoniazid occurs because the drug disrupts pyridoxine (vitamin B6) metabolism, leading to deficiency that impairs nerve function. Alcohol use makes this risk worse, so numbness, tingling, or other paresthesias in the feet (and sometimes hands) are a key warning sign. Reporting these symptoms promptly allows timely pyridoxine supplementation and adjustments if needed to prevent progression. Other adverse effects, such as vision changes (more linked to another TB drug) or abdominal pain from hepatotoxicity, are important but the described sensory symptoms are the classic early signal to address immediately.