Pyridoxine (vitamin B6)

Vitamins. Coenzyme

ATC code: A11HA02 (Pyridoxine (vitamin B6))

Brand names – drugs

Diclegis, Bonjesta

Brand names – supplements

NOW Foods Vitamin B-6, Solgar B-6 100 mg

Supplements are not tested in clinical trials and are not registered as medications.

Mechanism of action

Pyridoxine (vitamin B6) is phosphorylated in the body to the active form pyridoxal-5-phosphate (PLP), a cofactor for more than 100 enzymes mainly in amino acid metabolism: transaminases, decarboxylases (neurotransmitter synthesis: GABA, serotonin, dopamine, noradrenaline), and glycogen phosphorylase. Participates in haem and sphingomyelin synthesis. At pharmacological doses (above 200 mg daily) prolonged use causes dose-dependent sensory neuropathy.

Indications

Nausea and vomiting of pregnancy

First line

Pyridoxine 10–25 mg up to 4 times daily alone or with doxylamine (Diclegis/Bonjesta) is first-line for nausea and vomiting of pregnancy. ACOG 2018 recommends pyridoxine as initial pharmacotherapy after dietary measures fail. Cochrane 2015 showed clinically meaningful symptom reduction. Safe for the foetus and mother at doses up to 200 mg daily.

Sources

Pyridoxine-dependent epilepsy

First line

Pyridoxine 50–500 mg daily is the only disease-modifying therapy for the rare autosomal recessive pyridoxine-dependent epilepsy (ALDH7A1 mutations). A trial intravenous pyridoxine 100 mg with concurrent EEG monitoring is both diagnostic and therapeutic for resistant neonatal seizures. Therapy is lifelong. Brain 2021 provides international guidance.

Used in specialised paediatric neurology centres with confirmed genetic diagnosis.

Sources

Brain: Pyridoxine-dependent epilepsy: a clinical guideline (2021)

Vitamin B6 (pyridoxine) deficiency

First line

Pyridoxine 25–100 mg daily is first-line for confirmed vitamin B6 deficiency in adults. In patients on isoniazid (drug-induced neuropathy prevention): 25–50 mg daily concurrent pyridoxine. In patients on penicillamine, hydralazine, or cycloserine: similar doses. In infants with pyridoxine-dependent epilepsy: high-dose lifelong therapy.

Sources

ГРЛС: Пиридоксин – Государственный реестр лекарственных средств (2026)

Premenstrual syndrome

Not recommended

An old Cochrane review (1999) showed a weak effect of pyridoxine 50–100 mg daily on PMS symptoms. Newer systematic reviews have not confirmed clinically meaningful effects. ACOG does not include pyridoxine in first-line PMS therapy. Standard therapy: oral contraceptives, luteal-phase SSRIs, lifestyle change. High-dose pyridoxine for PMS carries neuropathy risk with prolonged use.

Sources

Cochrane: Vitamin B-6 (pyridoxine) and its combinations for premenstrual syndrome (1999)

Anti-aging and longevity (marketed indication)

Not recommended

Vitamin B6 for slowing ageing, extending lifespan, or supporting cognition in healthy people is not mentioned in international guidelines. Homocysteine-lowering therapy (B6, B9, B12) in patients without inherited homocysteine metabolism disorders has not shown an effect on cardiovascular outcomes or all-cause mortality in large RCTs. Long-term high-dose pyridoxine (above 200 mg daily) is dangerous due to sensory neuropathy.

Sources

Cochrane: Vitamin B-6 (pyridoxine) and its combinations for premenstrual syndrome (1999)

Practical notes

Timing and administration

Take regardless of meals. Well absorbed from the small intestine. With isoniazid, take concurrently or within 1 hour.

Dose titration

Adult RDA: 1.3–1.7 mg. Isoniazid prophylaxis: 25–50 mg daily. Deficiency treatment: 25–100 mg daily for 1–4 weeks. NVP: 10–25 mg up to 4 times daily. Pyridoxine-dependent epilepsy: 50–500 mg/day (paediatric dose). Upper tolerable intake level (UL): 100 mg daily long-term.

Monitoring

With long-term doses above 100 mg daily, regularly assess peripheral sensation (vibration, proprioception). Sensory neuropathy is the main risk of long-term high-dose use. Symptoms: distal limb paraesthesia, gait disturbance. After pyridoxine discontinuation, symptom regression is slow and may be incomplete in some patients.

Food and drinks

Dietary sources: chicken, fish (tuna, salmon), potatoes, bananas, chickpeas, pistachios. The RDA is easily met by an ordinary diet. Deficiency develops mainly with antagonist drugs (isoniazid, hydralazine, penicillamine, cycloserine), in chronic alcohol use, and in older adults on severely restricted diets.

Common myths

Myth: “B6 calms the nervous system and improves sleep”. Fact: the effect on the nervous system in non-deficient patients is not confirmed. The hypnotic-sedative claim in supplement marketing lacks scientific basis.

Myth: “high-dose B6 is safe”. Fact: doses above 200 mg daily long-term (more than 6 months) cause sensory neuropathy. Cases are reported at 100 mg daily over more than a year. This is the most dangerous vitamin with uncontrolled use.

Myth: “B6 treats PMS”. Fact: newer systematic reviews have not confirmed an effect. Standard PMS therapy: oral contraceptives, luteal-phase SSRIs, CBT – not B6.

Safety

Contraindications

Hypersensitivity to pyridoxine
Severe ischaemic heart disease (for high-dose parenteral administration)
Active peptic ulcer disease (relative)

Serious adverse effects

Sensory neuropathy with paraesthesia and ataxia with long-term (over 6 months) doses above 200 mg daily
Anaphylactic reactions (very rare)

Common adverse effects

Allergic reactions (urticaria, pruritus)
Skin rash

Uncommon adverse effects

Epigastric discomfort at high doses
Reduced gastric acid secretion

PregnancyFDA A

FDA category A at physiological doses. Use of 10–25 mg four times daily for nausea and vomiting of pregnancy is safe and encouraged by ACOG. Doses above 100 mg daily long-term in pregnancy are not recommended.

Breastfeeding

Transfers into breast milk at physiological amounts. Supplementation at the RDA is safe. High doses can suppress lactation – not recommended.