Pyridoxine (Vitamin B6)
Pyridoxine is a vitamin B6 precursor used for selected toxicities and uncommon deficiency states.
Group
Water-soluble vitamin; antidote
Mechanism of Action
Converted to pyridoxal phosphate, a coenzyme involved in amino-acid metabolism, haem synthesis and GABA production.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Isoniazid poisoning – unknown amount | 71 mg/kg | IV | Once | Infuse as a 5-10% solution over 30-60 minutes; source also describes bolus use. Known exposures require mg-for-mg pyridoxine/isoniazid matching instead. |
| Crimidine poisoning | 20 mg/kg | IV | Once | |
| Liposomal doxorubicin skin toxicity prevention | 50 mg/animal | PO | Every 8 h | Investigated during the pegylated-liposomal doxorubicin protocol; not a general nutritional dose. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Crimidine poisoning | 20 mg/kg | IV | Once |
Indications
- Isoniazid poisoning
- Crimidine poisoning
- Selected chemotherapy-associated skin toxicity
Contraindications
- Hypersensitivity; avoid prolonged excessive dosing.
Interactions
- Can reduce levodopa efficacy unless carbidopa is present.
- High doses may reduce phenobarbital or phenytoin concentrations.
- Isoniazid and several other drugs increase functional B6 requirements.
Adverse effects
- High or prolonged doses may cause sensory neuropathy and ataxia.
Toxicity
Discontinue excess exposure; neurologic recovery may be slow. Massive acute exposure can cause seizures.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Pyridoxine hydrochloride injection 100 mg/mL | Injection | 100 mg / mL | IV |
| Pyridoxine hydrochloride 50 mg tablet | Tablet | 50 mg / tablet | PO |
| Pyridoxine hydrochloride 100 mg tablet | Tablet | 100 mg / tablet | PO |
Monitoring and Administration
For known isoniazid ingestion, match pyridoxine dose in mg to the ingested isoniazid mg; this is an exposure-based calculation, not a standard mg/kg regimen.
Use a single-ingredient antidotal preparation rather than injectable B-complex vitamins. Protect injection from light and freezing.
Assess seizure control and neurologic recovery; do not mix with alkaline/oxidising solutions or iron salts.