Why is pyridoxine recommended with isoniazid?

• A. To prevent isoniazid-induced peripheral neuropathy.
• B. To enhance isoniazid bactericidal activity.
• C. To shorten treatment duration.
• D. To prevent hepatotoxicity.

Answer: (A)

Isoniazid can cause vitamin B6 deficiency, which leads to peripheral neuropathy. Pyridoxine (vitamin B6) supplementation replenishes the active cofactor, pyridoxal-5'-phosphate, that is depleted or inactivated by isoniazid. With enough B6 available, the enzymes needed for nerve function and neurotransmitter synthesis continue to work properly, protecting the peripheral nerves from damage. This protective effect happens without affecting the drug’s ability to kill the bacteria, and it does not shorten the treatment course or prevent hepatotoxicity. So, pyridoxine is given with isoniazid primarily to prevent isoniazid-induced peripheral neuropathy.