Recommended Dose of Pyridoxine for Prevention of Peripheral Neuropathy in Patients on Isoniazid
The recommended dose of pyridoxine (vitamin B6) for prevention of peripheral neuropathy in patients undergoing Anti-Tuberculosis Treatment (ATT) with isoniazid is 25-50 mg daily for high-risk patients. 1
Indications for Pyridoxine Supplementation
- Pyridoxine should be given with isoniazid to all persons at risk of neuropathy, including: 1
- Pregnant women
- Breastfeeding infants
- Persons infected with HIV
- Patients with diabetes
- Patients with alcoholism
- Patients with malnutrition
- Patients with chronic renal failure
- Elderly patients
Dosing Recommendations
- Standard prophylactic dose: 25-50 mg of pyridoxine daily for patients at risk of peripheral neuropathy 1
- Treatment dose: For patients who develop peripheral neuropathy while on isoniazid, experts recommend increasing the pyridoxine dose to 100 mg daily 1
- Lower doses (6-10 mg daily) have been shown to be effective in preventing neuropathy in some studies, but current guidelines recommend the higher dosage range for at-risk patients 2, 3, 4
Mechanism of Isoniazid-Induced Neuropathy
- Isoniazid competitively inhibits the action of pyridoxine in metabolic functions 5
- This leads to deficiency of pyridoxal phosphate, causing axonal degeneration and disruption of nerve fibers 6
- The neuropathy occurs more frequently in "slow inactivators" of isoniazid who maintain higher serum levels of the drug 2, 7
Clinical Presentation of Peripheral Neuropathy
- Initial symptoms include numbness and paresthesia in the extremities 6
- May progress to loss of distal sensation, motor ataxia, weakness, and loss of deep tendon reflexes if not treated 6
- Symptoms typically begin with sensory changes in a "stocking-glove" distribution 8
Monitoring Recommendations
- All patients on isoniazid should be instructed to report symptoms suggesting peripheral neuropathy immediately 1
- Patients at high risk should be monitored more closely for development of neuropathic symptoms 8, 6
- Regular clinical assessment for symptoms of peripheral neuropathy should be performed at follow-up visits 1
Important Considerations and Pitfalls
- Excessive doses of pyridoxine (>200 mg daily) should be avoided as they can themselves cause peripheral neuropathy 6
- Peripheral neuropathy is more common with higher doses of isoniazid (12.5-15.6 mg/kg body weight) compared to standard doses (5 mg/kg) 2, 7
- Patients with renal insufficiency may be at higher risk of pyridoxine toxicity and require careful monitoring 6
- The British Thoracic Society notes that pyridoxine supplementation is only advised for those at increased risk of neuropathy, not for all patients on isoniazid 1
By following these evidence-based recommendations for pyridoxine supplementation, clinicians can effectively prevent the development of isoniazid-induced peripheral neuropathy in patients undergoing anti-tuberculosis treatment.