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.
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.
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. 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.
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.
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.
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. 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.
Not recommended
— Anti-aging and longevity: 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.
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.
Transfers into breast milk at physiological amounts. Supplementation at the RDA is safe. High doses can suppress lactation – not recommended.
pyridoxine (vitamin B6) is evaluated for the following indications with varying evidence strength: Vitamin B6 (pyridoxine) deficiency (evidence tier A), Nausea and vomiting of pregnancy (evidence tier A), Pyridoxine-dependent epilepsy (evidence tier A). See the full indication matrix with dosing and citations above on this page.
Common side effects of pyridoxine (vitamin B6) (≥ 1 in 100): Allergic reactions (urticaria, pruritus), Skin rash. See the Safety section for uncommon and serious reactions.
FDA category 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.
Transfers into breast milk at physiological amounts. Supplementation at the RDA is safe. High doses can suppress lactation – not recommended.
pyridoxine (vitamin B6) is contraindicated in: Hypersensitivity to pyridoxine; Severe ischaemic heart disease (for high-dose parenteral administration); Active peptic ulcer disease (relative). Full list in the Safety section.
the effect on the nervous system in non-deficient patients is not confirmed. The hypnotic-sedative claim in supplement marketing lacks scientific basis.
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.
newer systematic reviews have not confirmed an effect. Standard PMS therapy: oral contraceptives, luteal-phase SSRIs, CBT – not B6.