Ans. (c) Vitamin B6Ref. KDT 6th ed. / 740-41* For patients who are on isoniazid; peripheral neuropathy is observed in 10-20% of patients given dosages greater than 5 mg/kg/d but is infrequently seen with the standard 300 mg adult dose.* Pyridoxine (Vit B6), 25-50 mg/d, is recommended for those with conditions predisposing to neuropathy, an adverse effect of isoniazid.* NOTE: Isoniazid as a single agent is also indicated for treatment of latent tuberculosis. The dosage is 300 mg/d (5 mg/kg/d) or 900 mg twice weekly for 9 months.