Pyridoxine
Vitamins
Vitamins
Vitamin B6. Prevents the nerve damage of isoniazid and is the antidote in isoniazid poisoning. Too much damages nerves.
Also called: vitamin B6
Quick facts
- Group
- Vitamins
- Target
- Pyridoxal 5'-phosphate, coenzyme of transamination and decarboxylation
- Used for
- Vitamin B6 deficiency from poor diet
- Key effects
- Upset stomach · Tingling or burning in the hands
- Monitor
- Tingling · Response in lab tests
- ATC
- A11HA02
No doses: the clinician sets them by the current guideline.
Mechanism of action
Pyridoxine is converted to pyridoxal phosphate, a step that needs riboflavin. Pyridoxal phosphate is the coenzyme for amino acid transamination, decarboxylation and deamination, the conversion of tryptophan and the breakdown of glycogen. Isoniazid depletes vitamin B6, which explains its neuropathy and, in overdose, its seizures.
- Pyridoxine → pyridoxal phosphate (needs riboflavin)
- PLP drives transamination and decarboxylation
- Replaces B6 lost to isoniazid; protects nerves
Indications
- Vitamin B6 deficiency from poor diet
- Drug-induced deficiency, such as with isoniazid
- Isoniazid poisoning (seizures) Isoniazid toxicity →
- Vitamin B6-dependent seizures and B6-responsive anaemia
- Nausea and vomiting of pregnancy
Adverse effects
Common
- Upset stomach, headache, sleepiness
- Tingling or burning in the hands and feet
- Low folic acid levels
Contraindications
- Sensitivity to pyridoxine or another ingredient
Key interactions
- Levodopa given alone
- Pyridoxine reduces its effect; this does not happen with levodopa plus carbidopa
- Isoniazid
- Depletes vitamin B6; pyridoxine is given to prevent neuropathy
- Oral contraceptives
- May increase the need for pyridoxine
What is monitored
- Tingling, numbness or unsteady gait (deficiency or excess)
- Response in lab tests, such as blood count in B6-responsive anaemia
Administration and safety
- Injection is IM or IV and is protected from light.
- The injection contains aluminium: care in kidney failure and premature neonates.
- Extended-release tablets are swallowed whole.
Pregnancy and breastfeeding
Requirements rise in pregnancy, and pyridoxine is sometimes used for nausea and vomiting of pregnancy.
Nursing care
- In patients starting isoniazid, check that pyridoxine has been considered, especially with malnutrition, alcohol use, diabetes or pregnancy.
- Ask about levodopa use.
- Teach the patient to report numbness or clumsiness, which can come from too much as well as too little B6.
Pharmacokinetics
- Metabolism
- Broken down in the liver to 4-pyridoxic acid
- Elimination
- 4-pyridoxic acid leaves in the urine
- Half-life
- Long, about 15–20 days
Test yourself
Think of the answer, then tap the question to see it.
Why is pyridoxine given with isoniazid?
Isoniazid depletes vitamin B6 and can cause peripheral neuropathy.
Which antiparkinson drug loses effect with pyridoxine?
Levodopa given alone (not with carbidopa).
What does too much vitamin B6 cause?
Sensory neuropathy: numbness and loss of coordination.
Connections
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - PYRIDOXINE HYDROCHLORIDE injection, solution (DailyMed (U.S. National Library of Medicine), 2019); Pyridoxine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Vitamin B6: MedlinePlus Medical Encyclopedia (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.