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Vitamin B6 Pregnancy: §4.6 verbatim: 'Data on exposed pregnancies indicate no adverse effects of pyridoxine in therapeutic doses on pregnancy or the health of the foetus or newborn child, or during lactation. Animal studies are insufficient with respects to effects on pregnancy, embiyonal/foetal development, parturition or postnatal development. Caution should be exercised when prescribing to pregnant women.' (Spelling as printed in the SPC.) No pregnancy category letter is assigned in the UK SPC.

Pyridoxine hydrochloride

Pyridoxine hydrochloride (vitamin B6) is used in haematology chiefly to treat pyridoxine-responsive sideroblastic anaemia and to prevent or correct deficiency, including isoniazid-induced deficiency.

Adult dose

Dose: ORAL 50 mg TABLETS ONLY — this bundle contains no parenteral pyridoxine labelling, so no IV dose is stated (see SCOPE in notes). §4.2 gives three indications, each quoted verbatim. IDIOPATHIC SIDEROBLASTIC ANAEMIA (the haematology indication for this page), adults: '100 to 400mg daily in divided doses'. PYRIDOXINE DEFICIENCY STATES, adults: '50 to 150mg daily in divided doses'. ISONIAZID-INDUCED PERIPHERAL NEURITIS, adults: treatment '50mg three times daily'; prophylaxis — 'Not suitable with this dosage form'. ELDERLY, all three indications: 'Dosage requirements appear to be similar to those for young adults'.
Route: Oral (50 mg film-coated tablets). This page also lists an intravenous route; no parenteral pyridoxine product appears anywhere in this bundle, so no IV dose, strength or infusion instruction is given here.
Frequency: In divided doses. Isoniazid-induced peripheral neuritis: three times daily. Idiopathic sideroblastic anaemia and deficiency states: 'daily in divided doses' — the SPC does not specify how many divisions.
Max: 400 mg daily in divided doses — the top of the idiopathic sideroblastic anaemia range and the highest figure anywhere in this SPC. It is NOT a ceiling for the other indications, which have lower ones: deficiency states 150 mg daily in divided doses, and isoniazid-induced peripheral neuritis 50 mg three times daily.
SCOPE — this record covers the oral 50 mg film-coated tablet only. The page's IV route is unsourced in this bundle and is deliberately left blank rather than inferred. The sideroblastic anaemia range matches this SPC; the other two do not. The SPC gives deficiency states as 50 to 150 mg daily in divided doses (not 20–50 mg three times daily), and for isoniazid PROPHYLAXIS it says only 'Not suitable with this dosage form' — it gives no 10 mg/day figure and no prophylaxis dose at all. ⚠️ SAFETY CEILING, §4.8 verbatim: 'Long term administration of large doses of pyridoxine is associated with the development of severe peripheral neuritis.' §4.4 verbatim: 'Do not exceed the stated dose.' INTERACTIONS, §4.5 verbatim: 'Many drugs may alter the metabolism or bioavailability of pyridoxine, including isoniazid, penicillamine and oral contraceptives, which may increase the requirements for pyridoxine'. And: 'Pyridoxine hydrochloride may reduce the effect of levodopa, a drug used in the treatment of Parkinsons Disease unless a dopa decarboxylase inhibitor is also given.'

Paediatric dose

NO PAEDIATRIC DOSE EXISTS IN THIS LABEL. §4.2 states 'Children: This presentation is not recommended' separately under each of its three indications — isoniazid-induced peripheral neuritis, idiopathic sideroblastic anaemia and deficiency states. dosePerKg is therefore deliberately null and the weight calculator is left unset; no mg/kg figure appears anywhere in this SPC. Paediatric pyridoxine dosing must be prescribed against a children's formulary using an age-appropriate preparation, not from this 50 mg tablet record.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • §4.3 quoted in full: 'Hypersensitivity to the active substance(s) or to any of the excipients listed in section 6.1.'

Side effects

  • §4.8 quoted in full: 'Long term administration of large doses of pyridoxine is associated with the development of severe peripheral neuritis.' The fetched §4.8 lists no other adverse reaction and assigns no frequency categories.

Monitoring

  • §4.4 verbatim: 'If symptoms persist or worsen, seek medical advice.'
  • §4.4 verbatim: 'Do not exceed the stated dose.'
  • §4.8: on long-term or high-dose treatment, review for sensory peripheral neuropathy — 'Long term administration of large doses of pyridoxine is associated with the development of severe peripheral neuritis.'
  • §4.5: review co-prescribed levodopa (effect may be reduced unless a dopa decarboxylase inhibitor is also given), and isoniazid, penicillamine or oral contraceptives, which may increase pyridoxine requirements.

Clinical monograph

How it works

It is converted to pyridoxal phosphate, a coenzyme for amino acid metabolism and an early step in haem synthesis (delta-aminolaevulinic acid formation), which can improve haemoglobinisation in responsive sideroblastic anaemia.

Prescribing in practice

  • Prolonged use of high doses can cause a peripheral sensory neuropathy, so avoid unnecessarily high or long-term dosing.
  • Only a subset of sideroblastic anaemias are pyridoxine-responsive, so review the haematological response and stop if there is no benefit.
  • It can reduce the efficacy of levodopa given without a dopa-decarboxylase inhibitor, so check concurrent therapy.

Monitoring

Monitor the full blood count and haemoglobin response in sideroblastic anaemia, and review for any sensory neuropathy with prolonged use.

Counselling the patient

  • Take as directed and do not exceed the recommended amount because excess can affect the nerves.
  • Report any numbness, tingling or unsteadiness in the hands or feet.
  • Continued treatment depends on whether the blood count improves.

Evidence & guidelines

Pyridoxine is the recognised treatment for pyridoxine-responsive sideroblastic anaemia and for preventing isoniazid-induced deficiency.

Reference: NICE; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Pathways